diff --git a/app/code/Magento/SalesRule/Helper/CartFixedDiscount.php b/app/code/Magento/SalesRule/Helper/CartFixedDiscount.php
index b1fda3e78672b..025f2c7215964 100644
--- a/app/code/Magento/SalesRule/Helper/CartFixedDiscount.php
+++ b/app/code/Magento/SalesRule/Helper/CartFixedDiscount.php
@@ -89,6 +89,31 @@ public function getDiscountAmount(
         );
     }
 
+    /**
+     * Get discount amount for item calculated proportionally based on already applied discount
+     *
+     * @param float $ruleDiscount
+     * @param float $qty
+     * @param float $baseItemPrice
+     * @param float $baseItemDiscountAmount
+     * @param float $baseRuleTotalsDiscount
+     * @param string $discountType
+     * @return float
+     */
+    public function getDiscountedAmountProportionally(
+        float $ruleDiscount,
+        float $qty,
+        float $baseItemPrice,
+        float $baseItemDiscountAmount,
+        float $baseRuleTotalsDiscount,
+        string $discountType
+    ): float {
+        $baseItemPriceTotal = $baseItemPrice * $qty - $baseItemDiscountAmount;
+        $ratio = $baseItemPriceTotal / $baseRuleTotalsDiscount;
+        $discountAmount = $this->deltaPriceRound->round($ruleDiscount * $ratio, $discountType);
+        return $discountAmount;
+    }
+
     /**
      * Get shipping discount amount
      *
@@ -186,10 +211,6 @@ public function getBaseRuleTotals(
             $baseRuleTotals = ($quote->getIsMultiShipping() && $isMultiShipping) ?
                 $this->getQuoteTotalsForMultiShipping($quote) :
                 $this->getQuoteTotalsForRegularShipping($address, $baseRuleTotals);
-        } else {
-            if ($quote->getIsMultiShipping() && $isMultiShipping) {
-                $baseRuleTotals = $quote->getBaseSubtotal();
-            }
         }
         return (float) $baseRuleTotals;
     }
diff --git a/app/code/Magento/SalesRule/Model/Quote/Discount.php b/app/code/Magento/SalesRule/Model/Quote/Discount.php
index a32fe249920b1..0663e57a0a0f8 100644
--- a/app/code/Magento/SalesRule/Model/Quote/Discount.php
+++ b/app/code/Magento/SalesRule/Model/Quote/Discount.php
@@ -11,6 +11,7 @@
 use Magento\Quote\Api\Data\AddressInterface;
 use Magento\Quote\Api\Data\ShippingAssignmentInterface;
 use Magento\Quote\Model\Quote;
+use Magento\Quote\Model\Quote\Address;
 use Magento\Quote\Model\Quote\Address\Total;
 use Magento\Quote\Model\Quote\Address\Total\AbstractTotal;
 use Magento\Quote\Model\Quote\Item;
@@ -20,8 +21,10 @@
 use Magento\SalesRule\Api\Data\RuleDiscountInterfaceFactory;
 use Magento\SalesRule\Model\Data\RuleDiscount;
 use Magento\SalesRule\Model\Discount\PostProcessorFactory;
+use Magento\SalesRule\Model\Rule;
 use Magento\SalesRule\Model\Validator;
 use Magento\Store\Model\StoreManagerInterface;
+use Magento\SalesRule\Model\RulesApplier;
 
 /**
  * Discount totals calculation model.
@@ -66,6 +69,16 @@ class Discount extends AbstractTotal
      */
     private $discountDataInterfaceFactory;
 
+    /**
+     * @var RulesApplier|null
+     */
+    private $rulesApplier;
+
+    /**
+     * @var array
+     */
+    private $addressDiscountAggregator = [];
+
     /**
      * @param ManagerInterface $eventManager
      * @param StoreManagerInterface $storeManager
@@ -73,6 +86,7 @@ class Discount extends AbstractTotal
      * @param PriceCurrencyInterface $priceCurrency
      * @param RuleDiscountInterfaceFactory|null $discountInterfaceFactory
      * @param DiscountDataInterfaceFactory|null $discountDataInterfaceFactory
+     * @param RulesApplier|null $rulesApplier
      */
     public function __construct(
         ManagerInterface $eventManager,
@@ -80,7 +94,8 @@ public function __construct(
         Validator $validator,
         PriceCurrencyInterface $priceCurrency,
         RuleDiscountInterfaceFactory $discountInterfaceFactory = null,
-        DiscountDataInterfaceFactory $discountDataInterfaceFactory = null
+        DiscountDataInterfaceFactory $discountDataInterfaceFactory = null,
+        RulesApplier $rulesApplier = null
     ) {
         $this->setCode(self::COLLECTOR_TYPE_CODE);
         $this->eventManager = $eventManager;
@@ -91,6 +106,8 @@ public function __construct(
             ?: ObjectManager::getInstance()->get(RuleDiscountInterfaceFactory::class);
         $this->discountDataInterfaceFactory = $discountDataInterfaceFactory
             ?: ObjectManager::getInstance()->get(DiscountDataInterfaceFactory::class);
+        $this->rulesApplier = $rulesApplier
+            ?: ObjectManager::getInstance()->get(RulesApplier::class);
     }
 
     /**
@@ -102,6 +119,7 @@ public function __construct(
      * @return $this
      * @SuppressWarnings(PHPMD.CyclomaticComplexity)
      * @SuppressWarnings(PHPMD.NPathComplexity)
+     * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
      */
     public function collect(
         Quote $quote,
@@ -109,81 +127,98 @@ public function collect(
         Total $total
     ) {
         parent::collect($quote, $shippingAssignment, $total);
-
         $store = $this->storeManager->getStore($quote->getStoreId());
+        /** @var Address $address */
         $address = $shippingAssignment->getShipping()->getAddress();
-
         if ($quote->currentPaymentWasSet()) {
             $address->setPaymentMethod($quote->getPayment()->getMethod());
         }
-
         $this->calculator->reset($address);
-
-        $items = $shippingAssignment->getItems();
-        if (!count($items)) {
+        $itemsAggregate = [];
+        foreach ($shippingAssignment->getItems() as $item) {
+            $itemId = $item->getId();
+            $itemsAggregate[$itemId] = $item;
+        }
+        $items = [];
+        foreach ($quote->getAllAddresses() as $quoteAddress) {
+            foreach ($quoteAddress->getAllItems() as $item) {
+                $items[] = $item;
+            }
+        }
+        if (!$items || !$itemsAggregate) {
             return $this;
         }
-
         $eventArgs = [
             'website_id' => $store->getWebsiteId(),
             'customer_group_id' => $quote->getCustomerGroupId(),
             'coupon_code' => $quote->getCouponCode(),
         ];
-
-        $this->calculator->init($store->getWebsiteId(), $quote->getCustomerGroupId(), $quote->getCouponCode());
-        $this->calculator->initTotals($items, $address);
-
         $address->setDiscountDescription([]);
-        $items = $this->calculator->sortItemsByPriority($items, $address);
         $address->getExtensionAttributes()->setDiscounts([]);
-        $addressDiscountAggregator = [];
-
-        /** @var Item $item */
+        $this->addressDiscountAggregator = [];
+        $address->setCartFixedRules([]);
+        $quote->setCartFixedRules([]);
         foreach ($items as $item) {
-            if ($item->getNoDiscount() || !$this->calculator->canApplyDiscount($item)) {
-                $item->setDiscountAmount(0);
-                $item->setBaseDiscountAmount(0);
-
-                // ensure my children are zeroed out
-                if ($item->getHasChildren() && $item->isChildrenCalculated()) {
-                    foreach ($item->getChildren() as $child) {
-                        $child->setDiscountAmount(0);
-                        $child->setBaseDiscountAmount(0);
-                    }
+            $this->rulesApplier->setAppliedRuleIds($item, []);
+            if ($item->getExtensionAttributes()) {
+                $item->getExtensionAttributes()->setDiscounts(null);
+            }
+            $item->setDiscountAmount(0);
+            $item->setBaseDiscountAmount(0);
+            $item->setDiscountPercent(0);
+            if ($item->getChildren() && $item->isChildrenCalculated()) {
+                foreach ($item->getChildren() as $child) {
+                    $child->setDiscountAmount(0);
+                    $child->setBaseDiscountAmount(0);
+                    $child->setDiscountPercent(0);
+                }
+            }
+        }
+        $this->calculator->init($store->getWebsiteId(), $quote->getCustomerGroupId(), $quote->getCouponCode());
+        $this->calculator->initTotals($items, $address);
+        $items = $this->calculator->sortItemsByPriority($items, $address);
+        $rules = $this->calculator->getRules($address);
+        /** @var Rule $rule */
+        foreach ($rules as $rule) {
+            /** @var Item $item */
+            foreach ($items as $item) {
+                if ($item->getNoDiscount() || !$this->calculator->canApplyDiscount($item) || $item->getParentItem()) {
+                    continue;
                 }
+                $eventArgs['item'] = $item;
+                $this->eventManager->dispatch('sales_quote_address_discount_item', $eventArgs);
+                $this->calculator->process($item, $rule);
+            }
+            $appliedRuleIds = $quote->getAppliedRuleIds() ? explode(',', $quote->getAppliedRuleIds()) : [];
+            if ($rule->getStopRulesProcessing() && in_array($rule->getId(), $appliedRuleIds)) {
+                break;
+            }
+            $this->calculator->initTotals($items, $address);
+        }
+        foreach ($items as $item) {
+            if (!isset($itemsAggregate[$item->getId()])) {
                 continue;
             }
-            // to determine the child item discount, we calculate the parent
             if ($item->getParentItem()) {
                 continue;
-            }
-
-            $eventArgs['item'] = $item;
-            $this->eventManager->dispatch('sales_quote_address_discount_item', $eventArgs);
-
-            if ($item->getHasChildren() && $item->isChildrenCalculated()) {
-                $this->calculator->process($item);
+            } elseif ($item->getHasChildren() && $item->isChildrenCalculated()) {
                 foreach ($item->getChildren() as $child) {
                     $eventArgs['item'] = $child;
                     $this->eventManager->dispatch('sales_quote_address_discount_item', $eventArgs);
                     $this->aggregateItemDiscount($child, $total);
                 }
-            } else {
-                $this->calculator->process($item);
-                $this->aggregateItemDiscount($item, $total);
             }
+            $this->aggregateItemDiscount($item, $total);
             if ($item->getExtensionAttributes()) {
-                $this->aggregateDiscountPerRule($item, $address, $addressDiscountAggregator);
+                $this->aggregateDiscountPerRule($item, $address);
             }
         }
-
         $this->calculator->prepareDescription($address);
         $total->setDiscountDescription($address->getDiscountDescription());
         $total->setSubtotalWithDiscount($total->getSubtotal() + $total->getDiscountAmount());
         $total->setBaseSubtotalWithDiscount($total->getBaseSubtotal() + $total->getBaseDiscountAmount());
         $address->setDiscountAmount($total->getDiscountAmount());
         $address->setBaseDiscountAmount($total->getBaseDiscountAmount());
-
         return $this;
     }
 
@@ -273,13 +308,11 @@ public function fetch(Quote $quote, Total $total)
      *
      * @param AbstractItem $item
      * @param AddressInterface $address
-     * @param array $addressDiscountAggregator
      * @return void
      */
     private function aggregateDiscountPerRule(
         AbstractItem $item,
-        AddressInterface $address,
-        array &$addressDiscountAggregator
+        AddressInterface $address
     ) {
         $discountBreakdown = $item->getExtensionAttributes()->getDiscounts();
         if ($discountBreakdown) {
@@ -288,15 +321,17 @@ private function aggregateDiscountPerRule(
                 $discount = $value->getDiscountData();
                 $ruleLabel = $value->getRuleLabel();
                 $ruleID = $value->getRuleID();
-                if (isset($addressDiscountAggregator[$ruleID])) {
+                if (isset($this->addressDiscountAggregator[$ruleID])) {
                     /** @var RuleDiscount $cartDiscount */
-                    $cartDiscount = $addressDiscountAggregator[$ruleID];
+                    $cartDiscount = $this->addressDiscountAggregator[$ruleID];
                     $discountData = $cartDiscount->getDiscountData();
-                    $discountData->setBaseAmount($discountData->getBaseAmount()+$discount->getBaseAmount());
-                    $discountData->setAmount($discountData->getAmount()+$discount->getAmount());
-                    $discountData->setOriginalAmount($discountData->getOriginalAmount()+$discount->getOriginalAmount());
+                    $discountData->setBaseAmount($discountData->getBaseAmount() + $discount->getBaseAmount());
+                    $discountData->setAmount($discountData->getAmount() + $discount->getAmount());
+                    $discountData->setOriginalAmount(
+                        $discountData->getOriginalAmount() + $discount->getOriginalAmount()
+                    );
                     $discountData->setBaseOriginalAmount(
-                        $discountData->getBaseOriginalAmount()+$discount->getBaseOriginalAmount()
+                        $discountData->getBaseOriginalAmount() + $discount->getBaseOriginalAmount()
                     );
                 } else {
                     $data = [
@@ -313,10 +348,10 @@ private function aggregateDiscountPerRule(
                     ];
                     /** @var RuleDiscount $cartDiscount */
                     $cartDiscount = $this->discountInterfaceFactory->create(['data' => $data]);
-                    $addressDiscountAggregator[$ruleID] = $cartDiscount;
+                    $this->addressDiscountAggregator[$ruleID] = $cartDiscount;
                 }
             }
         }
-        $address->getExtensionAttributes()->setDiscounts(array_values($addressDiscountAggregator));
+        $address->getExtensionAttributes()->setDiscounts(array_values($this->addressDiscountAggregator));
     }
 }
diff --git a/app/code/Magento/SalesRule/Model/Rule/Action/Discount/CartFixed.php b/app/code/Magento/SalesRule/Model/Rule/Action/Discount/CartFixed.php
index 0adeedc32f759..9794dc1628dae 100644
--- a/app/code/Magento/SalesRule/Model/Rule/Action/Discount/CartFixed.php
+++ b/app/code/Magento/SalesRule/Model/Rule/Action/Discount/CartFixed.php
@@ -79,11 +79,13 @@ public function calculate($rule, $item, $qty)
 
         $ruleTotals = $this->validator->getRuleItemTotalsInfo($rule->getId());
         $baseRuleTotals = $ruleTotals['base_items_price'] ?? 0.0;
+        $baseRuleTotalsDiscount = $ruleTotals['base_items_discount_amount'] ?? 0.0;
+        $ruleItemsCount = $ruleTotals['items_count'] ?? 0;
 
         $address = $item->getAddress();
+        $quote = $item->getQuote();
         $shippingMethod = $address->getShippingMethod();
         $isAppliedToShipping = (int) $rule->getApplyToShipping();
-        $quote = $item->getQuote();
         $ruleDiscount = (float) $rule->getDiscountAmount();
 
         $isMultiShipping = $this->cartFixedDiscountHelper->checkMultiShippingQuote($quote);
@@ -91,6 +93,7 @@ public function calculate($rule, $item, $qty)
         $baseItemPrice = $this->validator->getItemBasePrice($item);
         $itemOriginalPrice = $this->validator->getItemOriginalPrice($item);
         $baseItemOriginalPrice = $this->validator->getItemBaseOriginalPrice($item);
+        $baseItemDiscountAmount = (float) $item->getBaseDiscountAmount();
 
         $cartRules = $quote->getCartFixedRules();
         if (!isset($cartRules[$rule->getId()])) {
@@ -101,17 +104,17 @@ public function calculate($rule, $item, $qty)
 
         if ($availableDiscountAmount > 0) {
             $store = $quote->getStore();
-            if ($ruleTotals['items_count'] <= 1) {
-                $baseRuleTotals = $shippingMethod ?
-                    $this->cartFixedDiscountHelper
-                        ->getBaseRuleTotals(
-                            $isAppliedToShipping,
-                            $quote,
-                            $isMultiShipping,
-                            $address,
-                            $baseRuleTotals
-                        ) : $baseRuleTotals;
-                $maximumItemDiscount = $this->cartFixedDiscountHelper
+            $baseRuleTotals = $shippingMethod ?
+                $this->cartFixedDiscountHelper
+                    ->getBaseRuleTotals(
+                        $isAppliedToShipping,
+                        $quote,
+                        $isMultiShipping,
+                        $address,
+                        $baseRuleTotals
+                    ) : $baseRuleTotals;
+            if ($isAppliedToShipping) {
+                $baseDiscountAmount = $this->cartFixedDiscountHelper
                     ->getDiscountAmount(
                         $ruleDiscount,
                         $qty,
@@ -119,29 +122,22 @@ public function calculate($rule, $item, $qty)
                         $baseRuleTotals,
                         $discountType
                     );
-                $quoteAmount = $this->priceCurrency->convert($maximumItemDiscount, $store);
-                $baseDiscountAmount = min($baseItemPrice * $qty, $maximumItemDiscount);
-                $this->deltaPriceRound->reset($discountType);
             } else {
-                $baseRuleTotals = $shippingMethod ?
-                    $this->cartFixedDiscountHelper
-                        ->getBaseRuleTotals(
-                            $isAppliedToShipping,
-                            $quote,
-                            $isMultiShipping,
-                            $address,
-                            $baseRuleTotals
-                        ) : $baseRuleTotals;
-                $maximumItemDiscount =$this->cartFixedDiscountHelper
-                    ->getDiscountAmount(
+                $baseDiscountAmount = $this->cartFixedDiscountHelper
+                    ->getDiscountedAmountProportionally(
                         $ruleDiscount,
                         $qty,
                         $baseItemPrice,
-                        $baseRuleTotals,
+                        $baseItemDiscountAmount,
+                        $baseRuleTotals - $baseRuleTotalsDiscount,
                         $discountType
                     );
-                $quoteAmount = $this->priceCurrency->convert($maximumItemDiscount, $store);
-                $baseDiscountAmount = min($baseItemPrice * $qty, $maximumItemDiscount);
+            }
+            $discountAmount = $this->priceCurrency->convert($baseDiscountAmount, $store);
+            $baseDiscountAmount = min($baseItemPrice * $qty, $baseDiscountAmount);
+            if ($ruleItemsCount <= 1) {
+                $this->deltaPriceRound->reset($discountType);
+            } else {
                 $this->validator->decrementRuleItemTotalsCount($rule->getId());
             }
 
@@ -162,24 +158,24 @@ public function calculate($rule, $item, $qty)
                 $ruleTotals['items_count'] <= 1) {
                 $estimatedShippingAmount = (float) $address->getBaseShippingInclTax();
                 $shippingDiscountAmount = $this->cartFixedDiscountHelper->
-                                                getShippingDiscountAmount(
-                                                    $rule,
-                                                    $estimatedShippingAmount,
-                                                    $baseRuleTotals
-                                                );
+                    getShippingDiscountAmount(
+                        $rule,
+                        $estimatedShippingAmount,
+                        $baseRuleTotals
+                    );
                 $cartRules[$rule->getId()] -= $shippingDiscountAmount;
                 if ($cartRules[$rule->getId()] < 0.0) {
                     $baseDiscountAmount += $cartRules[$rule->getId()];
-                    $quoteAmount += $cartRules[$rule->getId()];
+                    $discountAmount += $cartRules[$rule->getId()];
                 }
             }
             if ($availableDiscountAmount <= 0) {
                 $this->deltaPriceRound->reset($discountType);
             }
 
-            $discountData->setAmount($this->priceCurrency->roundPrice(min($itemPrice * $qty, $quoteAmount)));
+            $discountData->setAmount($this->priceCurrency->roundPrice(min($itemPrice * $qty, $discountAmount)));
             $discountData->setBaseAmount($baseDiscountAmount);
-            $discountData->setOriginalAmount(min($itemOriginalPrice * $qty, $quoteAmount));
+            $discountData->setOriginalAmount(min($itemOriginalPrice * $qty, $discountAmount));
             $discountData->setBaseOriginalAmount($this->priceCurrency->roundPrice($baseItemOriginalPrice));
         }
         $quote->setCartFixedRules($cartRules);
diff --git a/app/code/Magento/SalesRule/Model/RulesApplier.php b/app/code/Magento/SalesRule/Model/RulesApplier.php
index cde8e5c065502..3652f22798c14 100644
--- a/app/code/Magento/SalesRule/Model/RulesApplier.php
+++ b/app/code/Magento/SalesRule/Model/RulesApplier.php
@@ -10,7 +10,6 @@
 use Magento\SalesRule\Model\Data\RuleDiscount;
 use Magento\SalesRule\Model\Quote\ChildrenValidationLocator;
 use Magento\Framework\App\ObjectManager;
-use Magento\SalesRule\Model\ResourceModel\Rule\Collection;
 use Magento\SalesRule\Model\Rule\Action\Discount\CalculatorFactory;
 use Magento\SalesRule\Model\Rule\Action\Discount\Data;
 use Magento\SalesRule\Model\Rule\Action\Discount\DataFactory;
@@ -99,7 +98,7 @@ public function __construct(
      * Apply rules to current order item
      *
      * @param AbstractItem $item
-     * @param Collection $rules
+     * @param array $rules
      * @param bool $skipValidation
      * @param mixed $couponCode
      * @return array
@@ -109,10 +108,6 @@ public function applyRules($item, $rules, $skipValidation, $couponCode)
     {
         $address = $item->getAddress();
         $appliedRuleIds = [];
-        $this->discountAggregator = [];
-        if ($item->getExtensionAttributes()) {
-            $item->getExtensionAttributes()->setDiscounts(null);
-        }
         /* @var $rule Rule */
         foreach ($rules as $rule) {
             if (!$this->validatorUtility->canProcessRule($rule, $address)) {
@@ -138,10 +133,6 @@ public function applyRules($item, $rules, $skipValidation, $couponCode)
 
             $this->applyRule($item, $rule, $address, $couponCode);
             $appliedRuleIds[$rule->getRuleId()] = $rule->getRuleId();
-
-            if ($rule->getStopRulesProcessing()) {
-                break;
-            }
         }
 
         return $appliedRuleIds;
@@ -270,10 +261,9 @@ private function setDiscountBreakdown($discountData, $item, $rule, $address)
             ];
             /** @var RuleDiscount $itemDiscount */
             $ruleDiscount = $this->discountInterfaceFactory->create(['data' => $data]);
-            $this->discountAggregator[] = $ruleDiscount;
-            $item->getExtensionAttributes()->setDiscounts($this->discountAggregator);
+            $this->discountAggregator[$item->getId()][$rule->getId()] = $ruleDiscount;
+            $item->getExtensionAttributes()->setDiscounts(array_values($this->discountAggregator[$item->getId()]));
             $parentItem = $item->getParentItem();
-
             if ($parentItem && $parentItem->getExtensionAttributes()) {
                 $this->aggregateDiscountBreakdown($discountData, $parentItem, $rule, $address);
             }
@@ -281,6 +271,14 @@ private function setDiscountBreakdown($discountData, $item, $rule, $address)
         return $this;
     }
 
+    /**
+     * Reset discount aggregator
+     */
+    public function resetDiscountAggregator()
+    {
+        $this->discountAggregator = [];
+    }
+
     /**
      * Add Discount Breakdown to existing discount data
      *
@@ -413,7 +411,7 @@ public function setAppliedRuleIds(AbstractItem $item, array $appliedRuleIds)
         $address = $item->getAddress();
         $quote = $item->getQuote();
 
-        $item->setAppliedRuleIds(join(',', $appliedRuleIds));
+        $item->setAppliedRuleIds($this->validatorUtility->mergeIds($item->getAppliedRuleIds(), $appliedRuleIds));
         $address->setAppliedRuleIds($this->validatorUtility->mergeIds($address->getAppliedRuleIds(), $appliedRuleIds));
         $quote->setAppliedRuleIds($this->validatorUtility->mergeIds($quote->getAppliedRuleIds(), $appliedRuleIds));
 
diff --git a/app/code/Magento/SalesRule/Model/Validator.php b/app/code/Magento/SalesRule/Model/Validator.php
index 7b3a6b15b7a32..26fb7ee721732 100644
--- a/app/code/Magento/SalesRule/Model/Validator.php
+++ b/app/code/Magento/SalesRule/Model/Validator.php
@@ -12,6 +12,7 @@
 use Magento\Quote\Model\Quote\Item\AbstractItem;
 use Magento\SalesRule\Helper\CartFixedDiscount;
 use Magento\SalesRule\Model\ResourceModel\Rule\CollectionFactory;
+use Magento\SalesRule\Model\ResourceModel\Rule\Collection as RulesCollection;
 
 /**
  * SalesRule Validator Model
@@ -31,7 +32,7 @@ class Validator extends \Magento\Framework\Model\AbstractModel
     /**
      * Rule source collection
      *
-     * @var \Magento\SalesRule\Model\ResourceModel\Rule\Collection
+     * @var RulesCollection
      */
     protected $_rules;
 
@@ -58,7 +59,7 @@ class Validator extends \Magento\Framework\Model\AbstractModel
     protected $_skipActionsValidation = false;
 
     /**
-     * Catalog data
+     * Catalog data helper
      *
      * @var \Magento\Catalog\Helper\Data|null
      */
@@ -169,11 +170,24 @@ public function init($websiteId, $customerGroupId, $couponCode)
     /**
      * Get rules collection for current object state
      *
+     * @deprecated use getRules
      * @param Address|null $address
-     * @return \Magento\SalesRule\Model\ResourceModel\Rule\Collection
+     * @return RulesCollection
      * @throws \Zend_Db_Select_Exception
      */
     protected function _getRules(Address $address = null)
+    {
+        return $this->getRules($address);
+    }
+
+    /**
+     * Get rules collection for current object state
+     *
+     * @param Address|null $address
+     * @return RulesCollection
+     * @throws \Zend_Db_Select_Exception
+     */
+    public function getRules(Address $address = null)
     {
         $addressId = $this->getAddressId($address);
         $key = $this->getWebsiteId() . '_'
@@ -240,7 +254,7 @@ public function setSkipActionsValidation($flag)
     public function canApplyRules(AbstractItem $item)
     {
         $address = $item->getAddress();
-        foreach ($this->_getRules($address) as $rule) {
+        foreach ($this->getRules($address) as $rule) {
             if (!$this->validatorUtility->canProcessRule($rule, $address) || !$rule->getActions()->validate($item)) {
                 return false;
             }
@@ -260,6 +274,7 @@ public function reset(Address $address)
         $this->validatorUtility->resetRoundingDeltas();
         $address->setBaseSubtotalWithDiscount($address->getBaseSubtotal());
         $address->setSubtotalWithDiscount($address->getSubtotal());
+        $this->rulesApplier->resetDiscountAggregator();
         if ($this->_isFirstTimeResetRun) {
             $address->setAppliedRuleIds('');
             $address->getQuote()->setAppliedRuleIds('');
@@ -273,22 +288,12 @@ public function reset(Address $address)
      * Quote item discount calculation process
      *
      * @param AbstractItem $item
+     * @param Rule $rule
      * @return $this
      * @throws \Zend_Db_Select_Exception
      */
-    public function process(AbstractItem $item)
+    public function process(AbstractItem $item, Rule $rule)
     {
-        $item->setDiscountAmount(0);
-        $item->setBaseDiscountAmount(0);
-        $item->setDiscountPercent(0);
-        if ($item->getChildren() && $item->isChildrenCalculated()) {
-            foreach ($item->getChildren() as $child) {
-                $child->setDiscountAmount(0);
-                $child->setBaseDiscountAmount(0);
-                $child->setDiscountPercent(0);
-            }
-        }
-
         $itemPrice = $this->getItemPrice($item);
         if ($itemPrice < 0) {
             return $this;
@@ -296,7 +301,7 @@ public function process(AbstractItem $item)
 
         $appliedRuleIds = $this->rulesApplier->applyRules(
             $item,
-            $this->_getRules($item->getAddress()),
+            [$rule],
             $this->_skipActionsValidation,
             $this->getCouponCode()
         );
@@ -326,7 +331,7 @@ public function processShippingAmount(Address $address)
         }
         $quote = $address->getQuote();
         $appliedRuleIds = [];
-        foreach ($this->_getRules($address) as $rule) {
+        foreach ($this->getRules($address) as $rule) {
             /* @var Rule $rule */
             if (!$rule->getApplyToShipping() || !$this->validatorUtility->canProcessRule($rule, $address)) {
                 continue;
@@ -429,43 +434,51 @@ public function processShippingAmount(Address $address)
      * @param mixed $items
      * @param Address $address
      * @return $this
+     * @SuppressWarnings(PHPMD.CyclomaticComplexity)
      * @throws \Zend_Validate_Exception
      * @throws \Zend_Db_Select_Exception
      */
     public function initTotals($items, Address $address)
     {
-        $address->setCartFixedRules([]);
-
         if (!$items) {
             return $this;
         }
 
         /** @var Rule $rule */
-        foreach ($this->_getRules($address) as $rule) {
-            if (Rule::CART_FIXED_ACTION == $rule->getSimpleAction()
-                && $this->validatorUtility->canProcessRule($rule, $address)
+        foreach ($this->getRules($address) as $rule) {
+            if (Rule::CART_FIXED_ACTION !== $rule->getSimpleAction()
+                || !$this->validatorUtility->canProcessRule($rule, $address)
             ) {
-                $ruleTotalItemsPrice = 0;
-                $ruleTotalBaseItemsPrice = 0;
-                $validItemsCount = 0;
-
-                foreach ($items as $item) {
-                    //Skipping child items to avoid double calculations
-                    if (!$this->isValidItemForRule($item, $rule)) {
-                        continue;
-                    }
-                    $qty = $this->validatorUtility->getItemQty($item, $rule);
-                    $ruleTotalItemsPrice += $this->getItemPrice($item) * $qty;
-                    $ruleTotalBaseItemsPrice += $this->getItemBasePrice($item) * $qty;
-                    $validItemsCount++;
+                continue;
+            }
+            $ruleTotalItemsPrice = 0;
+            $ruleTotalBaseItemsPrice = 0;
+            $ruleTotalItemsDiscountAmount = 0;
+            $ruleTotalBaseItemsDiscountAmount = 0;
+            $validItemsCount = 0;
+
+            foreach ($items as $item) {
+                if (!$this->isValidItemForRule($item, $rule)
+                    || ($item->getChildren() && $item->isChildrenCalculated())
+                    || $item->getNoDiscount()
+                ) {
+                    continue;
                 }
-
-                $this->_rulesItemTotals[$rule->getId()] = [
-                    'items_price' => $ruleTotalItemsPrice,
-                    'base_items_price' => $ruleTotalBaseItemsPrice,
-                    'items_count' => $validItemsCount,
-                ];
+                $qty = $this->validatorUtility->getItemQty($item, $rule);
+                $ruleTotalItemsPrice += $this->getItemPrice($item) * $qty;
+                $ruleTotalBaseItemsPrice += $this->getItemBasePrice($item) * $qty;
+                $ruleTotalItemsDiscountAmount += $item->getDiscountAmount();
+                $ruleTotalBaseItemsDiscountAmount += $item->getBaseDiscountAmount();
+                $validItemsCount++;
             }
+
+            $this->_rulesItemTotals[$rule->getId()] = [
+                'items_price' => $ruleTotalItemsPrice,
+                'items_discount_amount' => $ruleTotalItemsDiscountAmount,
+                'base_items_price' => $ruleTotalBaseItemsPrice,
+                'base_items_discount_amount' => $ruleTotalBaseItemsDiscountAmount,
+                'items_count' => $validItemsCount,
+            ];
         }
 
         return $this;
@@ -480,12 +493,6 @@ public function initTotals($items, Address $address)
      */
     private function isValidItemForRule(AbstractItem $item, Rule $rule)
     {
-        if ($item->getParentItemId()) {
-            return false;
-        }
-        if ($item->getParentItem()) {
-            return false;
-        }
         if (!$rule->getActions()->validate($item)) {
             return false;
         }
@@ -613,7 +620,7 @@ public function sortItemsByPriority($items, Address $address = null)
     {
         $itemsSorted = [];
         /** @var $rule Rule */
-        foreach ($this->_getRules($address) as $rule) {
+        foreach ($this->getRules($address) as $rule) {
             foreach ($items as $itemKey => $itemValue) {
                 if ($rule->getActions()->validate($itemValue)) {
                     unset($items[$itemKey]);
diff --git a/app/code/Magento/SalesRule/Test/Unit/Model/Quote/DiscountTest.php b/app/code/Magento/SalesRule/Test/Unit/Model/Quote/DiscountTest.php
index 5633bd788de86..5a7d6142a6d43 100644
--- a/app/code/Magento/SalesRule/Test/Unit/Model/Quote/DiscountTest.php
+++ b/app/code/Magento/SalesRule/Test/Unit/Model/Quote/DiscountTest.php
@@ -9,20 +9,24 @@
 
 use Magento\Framework\Api\ExtensionAttributesInterface;
 use Magento\Framework\Event\Manager;
+use Magento\Framework\Event\ManagerInterface;
 use Magento\Framework\Pricing\PriceCurrencyInterface;
-use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
 use Magento\Quote\Api\Data\ShippingAssignmentInterface;
 use Magento\Quote\Api\Data\ShippingInterface;
 use Magento\Quote\Model\Quote;
 use Magento\Quote\Model\Quote\Address;
 use Magento\Quote\Model\Quote\Address\Total;
 use Magento\Quote\Model\Quote\Item;
+use Magento\SalesRule\Api\Data\DiscountDataInterfaceFactory;
+use Magento\SalesRule\Api\Data\RuleDiscountInterfaceFactory;
 use Magento\SalesRule\Model\Quote\Discount;
 use Magento\SalesRule\Model\Rule\Action\Discount\Data;
 use Magento\SalesRule\Model\Rule\Action\Discount\DataFactory;
+use Magento\SalesRule\Model\RulesApplier;
 use Magento\SalesRule\Model\Validator;
 use Magento\Store\Model\Store;
-use Magento\Store\Model\StoreManager;
+use Magento\SalesRule\Model\Rule;
+use Magento\Store\Model\StoreManagerInterface;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
@@ -36,11 +40,6 @@ class DiscountTest extends TestCase
      */
     protected $discount;
 
-    /**
-     * @var ObjectManager
-     */
-    protected $objectManager;
-
     /**
      * @var MockObject
      */
@@ -71,13 +70,36 @@ class DiscountTest extends TestCase
      */
     private $discountFactory;
 
+    /**
+     * @var Rule|MockObject
+     */
+    private $rule;
+
+    /**
+     * @var RuleDiscountInterfaceFactory|MockObject
+     */
+    private $discountInterfaceFactoryMock;
+
+    /**
+     * @var DiscountDataInterfaceFactory|MockObject
+     */
+    private $discountDataInterfaceFactoryMock;
+
+    /**
+     * @var RulesApplier|MockObject
+     */
+    private $rulesApplierMock;
+
     protected function setUp(): void
     {
-        $this->objectManager = new ObjectManager($this);
-        $this->storeManagerMock = $this->createMock(StoreManager::class);
+        $this->storeManagerMock = $this->getMockForAbstractClass(StoreManagerInterface::class);
+        $this->eventManagerMock = $this->getMockForAbstractClass(ManagerInterface::class);
+        $this->discountInterfaceFactoryMock = $this->createMock(RuleDiscountInterfaceFactory::class);
+        $this->discountDataInterfaceFactoryMock = $this->createMock(DiscountDataInterfaceFactory::class);
+        $this->rulesApplierMock = $this->createMock(RulesApplier::class);
         $this->validatorMock = $this->getMockBuilder(Validator::class)
             ->disableOriginalConstructor()
-            ->setMethods(
+            ->onlyMethods(
                 [
                     'canApplyRules',
                     'reset',
@@ -88,6 +110,16 @@ protected function setUp(): void
                     'process',
                     'processShippingAmount',
                     'canApplyDiscount',
+                    'getRules',
+                    'prepareDescription'
+                ]
+            )
+            ->getMock();
+        $this->rule = $this->getMockBuilder(Rule::class)
+            ->disableOriginalConstructor()
+            ->addMethods(
+                [
+                    'getSimpleAction'
                 ]
             )
             ->getMock();
@@ -108,7 +140,7 @@ function ($argument) {
             ->getMock();
         $addressExtension = $this->getMockBuilder(
             ExtensionAttributesInterface::class
-        )->setMethods(['setDiscounts', 'getDiscounts'])->getMock();
+        )->addMethods(['setDiscounts', 'getDiscounts'])->getMockForAbstractClass();
         $addressExtension->method('getDiscounts')->willReturn([]);
         $addressExtension->expects($this->any())
             ->method('setDiscounts')
@@ -130,14 +162,14 @@ function ($argument) {
         );
 
         /** @var Discount $discount */
-        $this->discount = $this->objectManager->getObject(
-            Discount::class,
-            [
-                'storeManager' => $this->storeManagerMock,
-                'validator' => $this->validatorMock,
-                'eventManager' => $this->eventManagerMock,
-                'priceCurrency' => $priceCurrencyMock,
-            ]
+        $this->discount = new Discount(
+            $this->eventManagerMock,
+            $this->storeManagerMock,
+            $this->validatorMock,
+            $priceCurrencyMock,
+            $this->discountInterfaceFactoryMock,
+            $this->discountDataInterfaceFactoryMock,
+            $this->rulesApplierMock
         );
         $discountData = $this->getMockBuilder(Data::class)
             ->getMock();
@@ -151,29 +183,38 @@ public function testCollectItemNoDiscount()
     {
         $itemNoDiscount = $this->getMockBuilder(Item::class)
             ->addMethods(['getNoDiscount'])
-            ->onlyMethods(['getExtensionAttributes'])
+            ->onlyMethods(['getExtensionAttributes', 'getParentItem', 'getId'])
             ->disableOriginalConstructor()
             ->getMock();
         $itemExtension = $this->getMockBuilder(
             ExtensionAttributesInterface::class
-        )->setMethods(['setDiscounts', 'getDiscounts'])->getMock();
+        )->addMethods(['setDiscounts', 'getDiscounts'])->getMockForAbstractClass();
         $itemExtension->method('getDiscounts')->willReturn([]);
         $itemExtension->expects($this->any())
             ->method('setDiscounts')
             ->willReturn([]);
-        $itemNoDiscount->expects(
-            $this->any()
-        )->method('getExtensionAttributes')->willReturn($itemExtension);
+        $itemNoDiscount->expects($this->any())->method('getExtensionAttributes')->willReturn($itemExtension);
+        $itemNoDiscount->expects($this->any())->method('getId')->willReturn(1);
         $itemNoDiscount->expects($this->once())->method('getNoDiscount')->willReturn(true);
         $this->validatorMock->expects($this->once())->method('sortItemsByPriority')
             ->with([$itemNoDiscount], $this->addressMock)
             ->willReturnArgument(0);
+        $this->validatorMock->expects($this->once())->method('getRules')
+            ->with($this->addressMock)
+            ->willReturn([$this->rule]);
+        $this->rule->expects($this->any())->method('getSimpleAction')
+            ->willReturn(null);
         $storeMock = $this->getMockBuilder(Store::class)
             ->addMethods(['getStore'])
             ->disableOriginalConstructor()
             ->getMock();
         $this->storeManagerMock->expects($this->any())->method('getStore')->willReturn($storeMock);
-        $quoteMock = $this->createMock(Quote::class);
+        $quoteMock = $this->getMockBuilder(Quote::class)
+            ->onlyMethods(['getAllAddresses', 'getStoreId'])
+            ->disableOriginalConstructor()
+            ->getMock();
+        $quoteMock->expects($this->any())->method('getAllAddresses')->willReturn([$this->addressMock]);
+        $this->addressMock->expects($this->any())->method('getAllItems')->willReturn([$itemNoDiscount]);
         $this->addressMock->expects($this->any())->method('getQuote')->willReturn($quoteMock);
         $this->shippingAssignmentMock->expects($this->any())->method('getItems')->willReturn([$itemNoDiscount]);
         $this->addressMock->expects($this->any())->method('getShippingAmount')->willReturn(true);
@@ -190,16 +231,23 @@ public function testCollectItemHasParent()
     {
         $itemWithParentId = $this->getMockBuilder(Item::class)
             ->addMethods(['getNoDiscount'])
-            ->onlyMethods(['getParentItem'])
+            ->onlyMethods(['getParentItem', 'getId', 'getExtensionAttributes'])
             ->disableOriginalConstructor()
             ->getMock();
         $itemWithParentId->expects($this->once())->method('getNoDiscount')->willReturn(false);
-        $itemWithParentId->expects($this->once())->method('getParentItem')->willReturn(true);
+        $itemWithParentId->expects($this->any())->method('getId')->willReturn(1);
+        $itemWithParentId->expects($this->any())->method('getParentItem')->willReturn(true);
+        $itemWithParentId->expects($this->any())->method('getExtensionAttributes')->willReturn(false);
 
         $this->validatorMock->expects($this->any())->method('canApplyDiscount')->willReturn(true);
         $this->validatorMock->expects($this->any())->method('sortItemsByPriority')
             ->with([$itemWithParentId], $this->addressMock)
             ->willReturnArgument(0);
+        $this->validatorMock->expects($this->once())->method('getRules')
+            ->with($this->addressMock)
+            ->willReturn([$this->rule]);
+        $this->rule->expects($this->any())->method('getSimpleAction')
+            ->willReturn(null);
 
         $storeMock = $this->getMockBuilder(Store::class)
             ->addMethods(['getStore'])
@@ -207,7 +255,12 @@ public function testCollectItemHasParent()
             ->getMock();
         $this->storeManagerMock->expects($this->any())->method('getStore')->willReturn($storeMock);
 
-        $quoteMock = $this->createMock(Quote::class);
+        $quoteMock = $this->getMockBuilder(Quote::class)
+            ->onlyMethods(['getAllAddresses', 'getStoreId'])
+            ->disableOriginalConstructor()
+            ->getMock();
+        $quoteMock->expects($this->any())->method('getAllAddresses')->willReturn([$this->addressMock]);
+        $this->addressMock->expects($this->any())->method('getAllItems')->willReturn([$itemWithParentId]);
 
         $this->addressMock->expects($this->any())->method('getQuote')->willReturn($quoteMock);
         $this->addressMock->expects($this->any())->method('getShippingAmount')->willReturn(true);
@@ -224,35 +277,46 @@ public function testCollectItemHasNoChildren()
     {
         $itemWithChildren = $this->getMockBuilder(Item::class)
             ->disableOriginalConstructor()
-            ->setMethods(
+            ->onlyMethods(
                 [
-                    'getNoDiscount',
                     'getParentItem',
-                    'getHasChildren',
                     'isChildrenCalculated',
                     'getChildren',
                     'getExtensionAttributes',
+                    'getId',
+                ]
+            )->addMethods(
+                [
+                    'getNoDiscount',
+                    'getHasChildren',
                 ]
             )
             ->getMock();
         $itemExtension = $this->getMockBuilder(
             ExtensionAttributesInterface::class
-        )->setMethods(['setDiscounts', 'getDiscounts'])->getMock();
+        )->addMethods(['setDiscounts', 'getDiscounts', 'getId'])->getMock();
         $itemExtension->method('getDiscounts')->willReturn([]);
         $itemExtension->expects($this->any())
             ->method('setDiscounts')
             ->willReturn([]);
+        $itemExtension->expects($this->any())->method('getId')->willReturn(1);
         $itemWithChildren->expects(
             $this->any()
         )->method('getExtensionAttributes')->willReturn($itemExtension);
         $itemWithChildren->expects($this->once())->method('getNoDiscount')->willReturn(false);
-        $itemWithChildren->expects($this->once())->method('getParentItem')->willReturn(false);
+        $itemWithChildren->expects($this->any())->method('getParentItem')->willReturn(false);
         $itemWithChildren->expects($this->once())->method('getHasChildren')->willReturn(false);
+        $itemWithChildren->expects($this->any())->method('getId')->willReturn(2);
 
         $this->validatorMock->expects($this->any())->method('canApplyDiscount')->willReturn(true);
         $this->validatorMock->expects($this->once())->method('sortItemsByPriority')
             ->with([$itemWithChildren], $this->addressMock)
             ->willReturnArgument(0);
+        $this->validatorMock->expects($this->once())->method('getRules')
+            ->with($this->addressMock)
+            ->willReturn([$this->rule]);
+        $this->rule->expects($this->any())->method('getSimpleAction')
+            ->willReturn(null);
 
         $storeMock = $this->getMockBuilder(Store::class)
             ->disableOriginalConstructor()
@@ -261,8 +325,11 @@ public function testCollectItemHasNoChildren()
         $this->storeManagerMock->expects($this->any())->method('getStore')->willReturn($storeMock);
 
         $quoteMock = $this->getMockBuilder(Quote::class)
+            ->onlyMethods(['getAllAddresses', 'getStoreId'])
             ->disableOriginalConstructor()
             ->getMock();
+        $quoteMock->expects($this->any())->method('getAllAddresses')->willReturn([$this->addressMock]);
+        $this->addressMock->expects($this->any())->method('getAllItems')->willReturn([$itemWithChildren]);
         $this->addressMock->expects($this->any())->method('getQuote')->willReturn($quoteMock);
         $this->addressMock->expects($this->any())->method('getShippingAmount')->willReturn(true);
         $this->shippingAssignmentMock->expects($this->any())->method('getItems')->willReturn([$itemWithChildren]);
diff --git a/app/code/Magento/SalesRule/Test/Unit/Model/Rule/Action/Discount/CartFixedTest.php b/app/code/Magento/SalesRule/Test/Unit/Model/Rule/Action/Discount/CartFixedTest.php
index 276a308980683..1889febcedd38 100644
--- a/app/code/Magento/SalesRule/Test/Unit/Model/Rule/Action/Discount/CartFixedTest.php
+++ b/app/code/Magento/SalesRule/Test/Unit/Model/Rule/Action/Discount/CartFixedTest.php
@@ -121,9 +121,10 @@ protected function setUp(): void
             ->disableOriginalConstructor()
             ->getMock();
         $this->cartFixedDiscountHelper = $this->getMockBuilder(CartFixedDiscount::class)
-            ->setMethods([
+            ->onlyMethods([
                 'calculateShippingAmountWhenAppliedToShipping',
                 'getDiscountAmount',
+                'getDiscountedAmountProportionally',
                 'checkMultiShippingQuote',
                 'getQuoteTotalsForMultiShipping',
                 'getQuoteTotalsForRegularShipping',
@@ -170,7 +171,7 @@ public function testCalculate(array $shipping, array $ruleDetails): void
             );
         $this->cartFixedDiscountHelper
             ->expects($this->any())
-            ->method('getDiscountAmount')
+            ->method('getDiscountedAmountProportionally')
             ->will(
                 $this->returnValue(
                     $ruleDetails['discounted_amount']
diff --git a/app/code/Magento/SalesRule/Test/Unit/Model/RulesApplierTest.php b/app/code/Magento/SalesRule/Test/Unit/Model/RulesApplierTest.php
index 50824a87316cb..af6f41cee2294 100644
--- a/app/code/Magento/SalesRule/Test/Unit/Model/RulesApplierTest.php
+++ b/app/code/Magento/SalesRule/Test/Unit/Model/RulesApplierTest.php
@@ -98,7 +98,7 @@ protected function setUp(): void
      * @return void
      * @dataProvider dataProviderChildren
      */
-    public function testApplyRulesWhenRuleWithStopRulesProcessingIsUsed(
+    public function testApplyRules(
         bool $isChildren,
         bool $isContinue
     ): void {
@@ -116,30 +116,19 @@ public function testApplyRulesWhenRuleWithStopRulesProcessingIsUsed(
             ->with($this->anything())
             ->willReturn($discountData);
         /**
-         * @var Rule|MockObject $ruleWithStopFurtherProcessing
+         * @var Rule|MockObject $rule
          */
-        $ruleWithStopFurtherProcessing = $this->getMockBuilder(Rule::class)
+        $rule = $this->getMockBuilder(Rule::class)
             ->addMethods(['getCouponType', 'getRuleId'])
             ->onlyMethods(['getStoreLabel', 'getActions'])
             ->disableOriginalConstructor()
             ->getMock();
-        /**
-         * @var Rule|MockObject $ruleThatShouldNotBeRun
-         */
-        $ruleThatShouldNotBeRun = $this->getMockBuilder(Rule::class)
-            ->addMethods(['getStopRulesProcessing'])
-            ->disableOriginalConstructor()
-            ->getMock();
 
         $actionMock = $this->getMockBuilder(Collection::class)
             ->addMethods(['validate'])
             ->disableOriginalConstructor()
             ->getMock();
 
-        $ruleWithStopFurtherProcessing->setName('ruleWithStopFurtherProcessing');
-        $ruleThatShouldNotBeRun->setName('ruleThatShouldNotBeRun');
-        $rules = [$ruleWithStopFurtherProcessing, $ruleThatShouldNotBeRun];
-
         $item->setDiscountCalculationPrice($positivePrice);
         $item->setData('calculation_price', $positivePrice);
 
@@ -151,7 +140,7 @@ public function testApplyRulesWhenRuleWithStopRulesProcessingIsUsed(
             ->method('canProcessRule')
             ->willReturn(true);
 
-        $ruleWithStopFurtherProcessing->expects($this->atLeastOnce())
+        $rule->expects($this->atLeastOnce())
             ->method('getActions')
             ->willReturn($actionMock);
 
@@ -174,18 +163,14 @@ public function testApplyRulesWhenRuleWithStopRulesProcessingIsUsed(
         }
 
         if (!$isContinue || !$isChildren) {
-            $ruleWithStopFurtherProcessing->expects($this->any())
+            $rule->expects($this->any())
                 ->method('getRuleId')
                 ->willReturn($ruleId);
 
-            $this->applyRule($item, $ruleWithStopFurtherProcessing);
-
-            $ruleWithStopFurtherProcessing->setStopRulesProcessing(true);
-            $ruleThatShouldNotBeRun->expects($this->never())
-                ->method('getStopRulesProcessing');
+            $this->applyRule($item, $rule);
         }
 
-        $result = $this->rulesApplier->applyRules($item, $rules, $skipValidation, $couponCode);
+        $result = $this->rulesApplier->applyRules($item, [$rule], $skipValidation, $couponCode);
         $this->assertEquals($appliedRuleIds, $result);
     }
 
diff --git a/app/code/Magento/SalesRule/Test/Unit/Model/ValidatorTest.php b/app/code/Magento/SalesRule/Test/Unit/Model/ValidatorTest.php
index 993ee04a6aaf4..82ca394effff5 100644
--- a/app/code/Magento/SalesRule/Test/Unit/Model/ValidatorTest.php
+++ b/app/code/Magento/SalesRule/Test/Unit/Model/ValidatorTest.php
@@ -274,6 +274,7 @@ public function testProcess(): void
     {
         $negativePrice = -1;
 
+        $rule = $this->createMock(Rule::class);
         $this->item->setDiscountCalculationPrice($negativePrice);
         $this->item->setData('calculation_price', $negativePrice);
 
@@ -284,34 +285,7 @@ public function testProcess(): void
             $this->model->getCustomerGroupId(),
             $this->model->getCouponCode()
         );
-        $this->model->process($this->item);
-    }
-
-    /**
-     * @return void
-     */
-    public function testProcessWhenItemPriceIsNegativeDiscountsAreZeroed(): void
-    {
-        $negativePrice = -1;
-        $nonZeroDiscount = 123;
-        $this->model->init(
-            $this->model->getWebsiteId(),
-            $this->model->getCustomerGroupId(),
-            $this->model->getCouponCode()
-        );
-
-        $this->item->setDiscountCalculationPrice($negativePrice);
-        $this->item->setData('calculation_price', $negativePrice);
-
-        $this->item->setDiscountAmount($nonZeroDiscount);
-        $this->item->setBaseDiscountAmount($nonZeroDiscount);
-        $this->item->setDiscountPercent($nonZeroDiscount);
-
-        $this->model->process($this->item);
-
-        $this->assertEquals(0, $this->item->getDiscountAmount());
-        $this->assertEquals(0, $this->item->getBaseDiscountAmount());
-        $this->assertEquals(0, $this->item->getDiscountPercent());
+        $this->model->process($this->item, $rule);
     }
 
     /**
@@ -328,6 +302,7 @@ public function testApplyRulesThatAppliedRuleIdsAreCollected(): void
             $this->model->getCustomerGroupId(),
             $this->model->getCouponCode()
         );
+        $rule = $this->createMock(Rule::class);
 
         $this->item->setDiscountCalculationPrice($positivePrice);
         $this->item->setData('calculation_price', $positivePrice);
@@ -337,7 +312,7 @@ public function testApplyRulesThatAppliedRuleIdsAreCollected(): void
             ->method('applyRules')
             ->with(
                 $this->item,
-                $this->ruleCollection,
+                [$rule],
                 $this->anything(),
                 $this->anything()
             )
@@ -349,7 +324,7 @@ public function testApplyRulesThatAppliedRuleIdsAreCollected(): void
                 $expectedRuleIds
             );
 
-        $this->model->process($this->item);
+        $this->model->process($this->item, $rule);
     }
 
     /**
diff --git a/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products.php b/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products.php
new file mode 100644
index 0000000000000..00e7c35c44a80
--- /dev/null
+++ b/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products.php
@@ -0,0 +1,32 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\Checkout\Model\Type\Onepage;
+use Magento\Quote\Api\CartRepositoryInterface;
+use Magento\Quote\Api\Data\CartInterface;
+use Magento\Quote\Api\Data\CartInterfaceFactory;
+use Magento\TestFramework\Workaround\Override\Fixture\Resolver;
+use Magento\TestFramework\Helper\Bootstrap;
+use Magento\Catalog\Api\ProductRepositoryInterface;
+
+Resolver::getInstance()->requireDataFixture('Magento/Catalog/_files/multiple_products.php');
+
+$objectManager = Bootstrap::getObjectManager();
+/** @var ProductRepositoryInterface $productRepository */
+$productRepository = Bootstrap::getObjectManager()
+    ->create(ProductRepositoryInterface::class);
+/** @var CartRepositoryInterface $quoteRepository */
+$quoteRepository = $objectManager->get(CartRepositoryInterface::class);
+/** @var CartInterface $quote */
+$quote = $objectManager->get(CartInterfaceFactory::class)->create();
+$quote->setIsActive(true)
+    ->setStoreId(1)
+    ->setCheckoutMethod(Onepage::METHOD_GUEST)
+    ->setReservedOrderId('test_quote_with_simple_products');
+$quote->addProduct($productRepository->get('simple1'), 1);
+$quote->addProduct($productRepository->get('simple2'), 1);
+$quoteRepository->save($quote);
diff --git a/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products_rollback.php b/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products_rollback.php
new file mode 100644
index 0000000000000..b47beadb76ff1
--- /dev/null
+++ b/dev/tests/integration/testsuite/Magento/Checkout/_files/quote_with_simple_products_rollback.php
@@ -0,0 +1,28 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\TestFramework\Helper\Bootstrap;
+use Magento\TestFramework\Workaround\Override\Fixture\Resolver;
+use Magento\Quote\Model\ResourceModel\Quote\Collection;
+use Magento\Quote\Model\Quote;
+use Magento\Framework\Registry;
+
+/** @var Registry $registry */
+$registry = Bootstrap::getObjectManager()->get(Registry::class);
+$registry->unregister('isSecureArea');
+$registry->register('isSecureArea', true);
+
+/** @var $order Quote */
+$quoteCollection = Bootstrap::getObjectManager()->create(Collection::class);
+foreach ($quoteCollection as $quote) {
+    $quote->delete();
+}
+
+Resolver::getInstance()->requireDataFixture('Magento/Catalog/_files/multiple_products_rollback.php');
+
+$registry->unregister('isSecureArea');
+$registry->register('isSecureArea', false);
diff --git a/dev/tests/integration/testsuite/Magento/SalesRule/Model/Rule/Action/Discount/CartFixedTest.php b/dev/tests/integration/testsuite/Magento/SalesRule/Model/Rule/Action/Discount/CartFixedTest.php
index 7ddb38ac94e5d..39b67e5c60214 100644
--- a/dev/tests/integration/testsuite/Magento/SalesRule/Model/Rule/Action/Discount/CartFixedTest.php
+++ b/dev/tests/integration/testsuite/Magento/SalesRule/Model/Rule/Action/Discount/CartFixedTest.php
@@ -427,7 +427,7 @@ public function testMultishipping(
     public function multishippingDataProvider(): array
     {
         return [
-            'Discount < 1stOrderSubtotal: only 1st order gets discount' => [
+            'Discount $5 proportionally spread between products' => [
                 5,
                 [
                     'subtotal' => 10.00,
@@ -443,54 +443,12 @@ public function multishippingDataProvider(): array
                 ],
                 [
                     'subtotal' => 5.00,
-                    'discount_amount' => -5.00,
-                    'shipping_amount' => 0.00,
-                    'grand_total' => 0.00,
-                ]
-            ],
-            'Discount = 1stOrderSubtotal: only 1st order gets discount' => [
-                10,
-                [
-                    'subtotal' => 10.00,
-                    'discount_amount' => -2.8600,
-                    'shipping_amount' => 5.00,
-                    'grand_total' => 12.1400,
-                ],
-                [
-                    'subtotal' => 20.00,
-                    'discount_amount' => -5.71,
-                    'shipping_amount' => 5.00,
-                    'grand_total' => 19.2900,
-                ],
-                [
-                    'subtotal' => 5.00,
-                    'discount_amount' => -5.00,
+                    'discount_amount' => -0.71,
                     'shipping_amount' => 0.00,
-                    'grand_total' => 0.00,
+                    'grand_total' => 4.2900,
                 ]
             ],
-            'Discount > 1stOrderSubtotal: 1st order get 100% discount and 2nd order get the remaining discount' => [
-                15,
-                [
-                    'subtotal' => 10.00,
-                    'discount_amount' => -4.2900,
-                    'shipping_amount' => 5.00,
-                    'grand_total' => 10.71,
-                ],
-                [
-                    'subtotal' => 20.00,
-                    'discount_amount' => -8.5700,
-                    'shipping_amount' => 5.00,
-                    'grand_total' => 16.43,
-                ],
-                [
-                    'subtotal' => 5.00,
-                    'discount_amount' => -5.00,
-                    'shipping_amount' => 0.00,
-                    'grand_total' => 0.00,
-                ]
-            ],
-            'Discount = 1stOrderSubtotal + 2ndOrderSubtotal: 1st order and 2nd order get 100% discount' => [
+            'Discount $30 proportionally spread between products' => [
                 30,
                 [
                     'subtotal' => 10.00,
@@ -506,36 +464,67 @@ public function multishippingDataProvider(): array
                 ],
                 [
                     'subtotal' => 5.00,
-                    'discount_amount' => -5.00,
+                    'discount_amount' => -4.29,
                     'shipping_amount' => 0.00,
-                    'grand_total' => 0.00,
+                    'grand_total' => 0.7100,
                 ]
             ],
-            'Discount > 1stOrdSubtotal + 2ndOrdSubtotal: 1st order and 2nd order get 100% discount'
-            . ' and 3rd order get remaining discount' => [
-                31,
+            'Discount $50 which is more then all subtotals combined proportionally spread between products' => [
+                50,
                 [
                     'subtotal' => 10.00,
-                    'discount_amount' => -8.8600,
+                    'discount_amount' => -10.0000,
                     'shipping_amount' => 5.00,
-                    'grand_total' => 6.14,
+                    'grand_total' => 5.0000,
                 ],
                 [
                     'subtotal' => 20.00,
-                    'discount_amount' => -17.7100,
+                    'discount_amount' => -20.0000,
                     'shipping_amount' => 5.00,
-                    'grand_total' => 7.29,
+                    'grand_total' => 5.0000,
                 ],
                 [
                     'subtotal' => 5.00,
                     'discount_amount' => -5.00,
                     'shipping_amount' => 0.00,
-                    'grand_total' => 0.00,
+                    'grand_total' => 0.0000,
                 ]
-            ]
+            ],
         ];
     }
 
+    /**
+     * @magentoAppIsolation enabled
+     * @magentoDataFixture Magento/SalesRule/_files/cart_rule_50_percent_off_no_condition.php
+     * @magentoDataFixture Magento/SalesRule/_files/cart_fixed_10_discount.php
+     * @magentoDataFixture Magento/Checkout/_files/quote_with_simple_products.php
+     * @return void
+     */
+    public function testDiscountsWhenByPercentRuleAppliedFirstAndCartFixedRuleSecond(): void
+    {
+        $totalDiscount = -20.99;
+        $discounts = [
+            'simple1' => 5.72,
+            'simple2' => 15.27,
+        ];
+        $quote = $this->getQuote('test_quote_with_simple_products');
+        $quote->setCouponCode('2?ds5!2d');
+        $quote->collectTotals();
+        $this->quoteRepository->save($quote);
+        $this->assertEquals(21.98, $quote->getBaseSubtotal());
+        $this->assertEquals($totalDiscount, $quote->getShippingAddress()->getDiscountAmount());
+        $items = $quote->getAllItems();
+        $this->assertCount(2, $items);
+        $item = array_shift($items);
+        $this->assertEquals('simple1', $item->getSku());
+        $this->assertEquals(5.99, $item->getPrice());
+        $this->assertEquals($discounts[$item->getSku()], $item->getDiscountAmount());
+        $item = array_shift($items);
+        $this->assertEquals('simple2', $item->getSku());
+        $this->assertEquals(15.99, $item->getPrice());
+        $this->assertEquals($discounts[$item->getSku()], $item->getDiscountAmount());
+    }
+
     /**
      * Get list of orders by quote id.
      *
diff --git a/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount.php b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount.php
new file mode 100644
index 0000000000000..cc69733b37c16
--- /dev/null
+++ b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount.php
@@ -0,0 +1,38 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\Customer\Model\GroupManagement;
+use Magento\SalesRule\Model\ResourceModel\Rule as RuleResourceModel;
+use Magento\SalesRule\Model\Rule;
+use Magento\Store\Model\StoreManagerInterface;
+use Magento\TestFramework\Helper\Bootstrap;
+
+$objectManager = Bootstrap::getObjectManager();
+
+/** @var Rule $salesRule */
+$salesRule = $objectManager->create(Rule::class);
+$salesRule->setData(
+    [
+        'name' => '10$ fixed discount on whole cart',
+        'is_active' => 1,
+        'customer_group_ids' => [GroupManagement::NOT_LOGGED_IN_ID],
+        'coupon_type' => Rule::COUPON_TYPE_NO_COUPON,
+        'conditions' => [],
+        'simple_action' => Rule::CART_FIXED_ACTION,
+        'discount_amount' => 10,
+        'discount_step' => 10,
+        'stop_rules_processing' => 0,
+        'website_ids' => [
+            $objectManager->get(StoreManagerInterface::class)->getWebsite()->getId(),
+        ],
+        'store_labels' => [
+            'store_id' => 0,
+            'store_label' => '10$ fixed discount on whole cart',
+        ]
+    ]
+);
+$objectManager->get(RuleResourceModel::class)->save($salesRule);
diff --git a/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount_rollback.php b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount_rollback.php
new file mode 100644
index 0000000000000..431104c993458
--- /dev/null
+++ b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_fixed_10_discount_rollback.php
@@ -0,0 +1,36 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+use Magento\Framework\Api\SearchCriteriaBuilder;
+use Magento\Framework\Registry;
+use Magento\SalesRule\Api\RuleRepositoryInterface;
+use Magento\SalesRule\Model\Rule;
+use Magento\TestFramework\Helper\Bootstrap;
+
+$objectManager = Bootstrap::getObjectManager();
+
+/** @var Registry $registry */
+$registry = $objectManager->get(Registry::class);
+$registry->unregister('isSecureArea');
+$registry->register('isSecureArea', true);
+
+/** @var SearchCriteriaBuilder $searchCriteriaBuilder */
+$searchCriteriaBuilder = $objectManager->get(SearchCriteriaBuilder::class);
+$searchCriteria = $searchCriteriaBuilder->addFilter('name', '10$ fixed discount on whole cart')
+    ->create();
+/** @var RuleRepositoryInterface $ruleRepository */
+$ruleRepository = $objectManager->get(RuleRepositoryInterface::class);
+$items = $ruleRepository->getList($searchCriteria)
+    ->getItems();
+/** @var Rule $salesRule */
+$salesRule = array_pop($items);
+if ($salesRule !== null) {
+    $ruleRepository->deleteById($salesRule->getRuleId());
+}
+
+$registry->unregister('isSecureArea');
+$registry->register('isSecureArea', false);
diff --git a/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_rule_50_percent_off_no_condition.php b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_rule_50_percent_off_no_condition.php
index 77178abdb2384..de6dff7194ac3 100644
--- a/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_rule_50_percent_off_no_condition.php
+++ b/dev/tests/integration/testsuite/Magento/SalesRule/_files/cart_rule_50_percent_off_no_condition.php
@@ -24,7 +24,7 @@
         'simple_action' => 'by_percent',
         'discount_amount' => 50,
         'discount_step' => 0,
-        'stop_rules_processing' => 1,
+        'stop_rules_processing' => 0,
         'website_ids' => [
             \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->get(
                 \Magento\Store\Model\StoreManagerInterface::class