diff --git a/ZUGFeRD/InvoiceDescriptor21Writer.cs b/ZUGFeRD/InvoiceDescriptor21Writer.cs
index 8073fb4b..a064a79f 100644
--- a/ZUGFeRD/InvoiceDescriptor21Writer.cs
+++ b/ZUGFeRD/InvoiceDescriptor21Writer.cs
@@ -1178,37 +1178,37 @@ private void _writeOptionalLegalOrganization(ProfileAwareXmlTextWriter writer, s
                     // all profiles
                     break;
                 case PartyTypes.ShipToTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.UltimateShipToTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.ShipFromTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.InvoiceeTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.PayeeTradeParty:
                     // all profiles
                     break;
                 case PartyTypes.SalesAgentTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.BuyerTaxRepresentativeTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.ProductEndUserTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.BuyerAgentTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.InvoicerTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.PayerTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; } // extended profile only
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 default:
                     return;
@@ -1258,37 +1258,37 @@ private void _writeOptionalParty(ProfileAwareXmlTextWriter writer, PartyTypes pa
                 case PartyTypes.BuyerTradeParty:
                     break;
                 case PartyTypes.ShipToTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.UltimateShipToTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.ShipFromTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.InvoiceeTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.PayeeTradeParty:
                     if (this.Descriptor.Profile == Profile.Minimum) { return; } // party is written for all profiles but minimum
                     break;
                 case PartyTypes.SalesAgentTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.BuyerTaxRepresentativeTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.ProductEndUserTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.BuyerAgentTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.InvoicerTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 case PartyTypes.PayerTradeParty:
-                    if (this.Descriptor.Profile != Profile.Extended) { return; }
+                    if ((this.Descriptor.Profile != Profile.Extended) && (this.Descriptor.Profile != Profile.XRechnung1) && (this.Descriptor.Profile != Profile.XRechnung)) { return; } // extended, XRechnung1, XRechnung profile only
                     break;
                 default:
                     return;
@@ -1368,11 +1368,7 @@ private void _writeOptionalParty(ProfileAwareXmlTextWriter writer, PartyTypes pa
                 }
 
                 _writeOptionalLegalOrganization(writer, "ram:SpecifiedLegalOrganization", party.SpecifiedLegalOrganization, partyType);
-
-                if (contact != null)
-                {
-                    _writeOptionalContact(writer, "ram:DefinedTradeContact", contact, Profile.Extended | Profile.XRechnung1 | Profile.XRechnung);
-                }
+                _writeOptionalContact(writer, "ram:DefinedTradeContact", contact, Profile.Extended | Profile.XRechnung1 | Profile.XRechnung);
 
                 writer.WriteStartElement("ram:PostalTradeAddress");
                 writer.WriteElementString("ram:PostcodeCode", party.Postcode); // BT-53
@@ -1424,43 +1420,46 @@ private void _writeOptionalParty(ProfileAwareXmlTextWriter writer, PartyTypes pa
 
         private void _writeOptionalContact(ProfileAwareXmlTextWriter writer, string contactTag, Contact contact, Profile profile = Profile.Unknown)
         {
-            if (contact != null)
+            if (contact == null)
             {
-                writer.WriteStartElement(contactTag, profile);
+                return;
+            }
 
-                if (!String.IsNullOrEmpty(contact.Name))
-                {
-                    writer.WriteElementString("ram:PersonName", contact.Name);
-                }
 
-                if (!String.IsNullOrEmpty(contact.OrgUnit))
-                {
-                    writer.WriteElementString("ram:DepartmentName", contact.OrgUnit);
-                }
+            writer.WriteStartElement(contactTag, profile);
 
-                if (!String.IsNullOrEmpty(contact.PhoneNo))
-                {
-                    writer.WriteStartElement("ram:TelephoneUniversalCommunication");
-                    writer.WriteElementString("ram:CompleteNumber", contact.PhoneNo);
-                    writer.WriteEndElement();
-                }
+            if (!String.IsNullOrEmpty(contact.Name))
+            {
+                writer.WriteElementString("ram:PersonName", contact.Name);
+            }
 
-                if (!String.IsNullOrEmpty(contact.FaxNo))
-                {
-                    writer.WriteStartElement("ram:FaxUniversalCommunication", ALL_PROFILES ^ (Profile.XRechnung1 | Profile.XRechnung));
-                    writer.WriteElementString("ram:CompleteNumber", contact.FaxNo);
-                    writer.WriteEndElement();
-                }
+            if (!String.IsNullOrEmpty(contact.OrgUnit))
+            {
+                writer.WriteElementString("ram:DepartmentName", contact.OrgUnit);
+            }
 
-                if (!String.IsNullOrEmpty(contact.EmailAddress))
-                {
-                    writer.WriteStartElement("ram:EmailURIUniversalCommunication");
-                    writer.WriteElementString("ram:URIID", contact.EmailAddress);
-                    writer.WriteEndElement();
-                }
+            if (!String.IsNullOrEmpty(contact.PhoneNo))
+            {
+                writer.WriteStartElement("ram:TelephoneUniversalCommunication");
+                writer.WriteElementString("ram:CompleteNumber", contact.PhoneNo);
+                writer.WriteEndElement();
+            }
+
+            if (!String.IsNullOrEmpty(contact.FaxNo))
+            {
+                writer.WriteStartElement("ram:FaxUniversalCommunication", ALL_PROFILES ^ (Profile.XRechnung1 | Profile.XRechnung));
+                writer.WriteElementString("ram:CompleteNumber", contact.FaxNo);
+                writer.WriteEndElement();
+            }
 
+            if (!String.IsNullOrEmpty(contact.EmailAddress))
+            {
+                writer.WriteStartElement("ram:EmailURIUniversalCommunication");
+                writer.WriteElementString("ram:URIID", contact.EmailAddress);
                 writer.WriteEndElement();
             }
+
+            writer.WriteEndElement();
         } // !_writeOptionalContact()
 
 
diff --git a/ZUGFeRD/ZUGFeRD.csproj b/ZUGFeRD/ZUGFeRD.csproj
index 5cbabf85..a70a8842 100644
--- a/ZUGFeRD/ZUGFeRD.csproj
+++ b/ZUGFeRD/ZUGFeRD.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;net461;net480</TargetFrameworks>
-    <Version>12.3.0</Version>
+    <Version>12.3.1</Version>
     <Authors>Stephan Stapel</Authors>
     <Company>s2 industries</Company>
     <Description>ZUGFeRD and it's successor Factur-X/ XRechnung are initiatives from German (respectively European) government to foster electronic invoices.
@@ -22,15 +22,16 @@ https://github.com/stephanstapel/ZUGFeRD-csharp</Description>
     <PackageProjectUrl>https://github.com/stephanstapel/ZUGFeRD-csharp/</PackageProjectUrl>
     <PackageTags>zugferd xml</PackageTags>
     <Copyright>Stephan Stapel, s2 industries, 2023</Copyright>
-    <AssemblyVersion>12.3.0</AssemblyVersion>
+    <AssemblyVersion>12.3.1</AssemblyVersion>
     <AssemblyTrademark>http://www.s2-industries.com</AssemblyTrademark>
-    <FileVersion>12.3.0.0</FileVersion>
+    <FileVersion>12.3.1.0</FileVersion>
     <PackageRequireLicenseAcceptance>true</PackageRequireLicenseAcceptance>
     <AssemblyName>s2industries.ZUGFeRD</AssemblyName>
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>ZUGFeRD.snk</AssemblyOriginatorKeyFile>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
-    <PackageReleaseNotes>12.3.0: enhanced standard conformance for all party types</PackageReleaseNotes>
+    <PackageReleaseNotes>12.3.1: bug fix for all party types
+12.3.0: enhanced standard conformance for all party types</PackageReleaseNotes>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <PackageId>ZUGFeRD-csharp</PackageId>
     <PackageReadmeFile>README.md</PackageReadmeFile>