diff --git a/src/Apps/W1/ExpenseAgent/app/src/APIs/ExpenseUsersAPI.Page.al b/src/Apps/W1/ExpenseAgent/app/src/APIs/ExpenseUsersAPI.Page.al
index 2fc6cdac2ab..28455c35f00 100644
--- a/src/Apps/W1/ExpenseAgent/app/src/APIs/ExpenseUsersAPI.Page.al
+++ b/src/Apps/W1/ExpenseAgent/app/src/APIs/ExpenseUsersAPI.Page.al
@@ -135,9 +135,12 @@ page 6918 "Expense Users API"
         // and blocks sign-in there. Apply the constraint in FilterGroup 2 so it
         // AND-combines with any caller-supplied $filter on Employee No., rather
         // than replacing it in the default FilterGroup 0.
+        // The same applies when the employee posting group was removed from the
+        // employee after the expense user was linked.
         OriginalFilterGroup := Rec.FilterGroup();
         Rec.FilterGroup(2);
         Rec.SetFilter("Employee No.", '<>%1', '');
+        Rec.SetFilter("Employee Posting Group", '<>%1', '');
         Rec.FilterGroup(OriginalFilterGroup);
     end;
 }
\ No newline at end of file
diff --git a/src/Apps/W1/ExpenseAgent/app/src/MasterData/Tables/ExpenseUser.Table.al b/src/Apps/W1/ExpenseAgent/app/src/MasterData/Tables/ExpenseUser.Table.al
index 4af2e4245a7..3eab8fd285b 100644
--- a/src/Apps/W1/ExpenseAgent/app/src/MasterData/Tables/ExpenseUser.Table.al
+++ b/src/Apps/W1/ExpenseAgent/app/src/MasterData/Tables/ExpenseUser.Table.al
@@ -38,6 +38,11 @@ table 6923 "Expense User"
                 if Rec."Employee No." <> '' then begin
                     Employee.Get("Employee No.");
 
+                    if Employee."Employee Posting Group" = '' then
+                        Error(
+                            EmployeePostingGroupMissingErr,
+                            Employee.TableCaption(), Employee."No.", Rec.TableCaption(), Employee.FieldCaption("Employee Posting Group"));
+
                     CheckDuplicateEmployeeNo();
 
                     if ConfirmOverwriteExpenseUserInformation(Employee) then begin
@@ -147,6 +152,14 @@ table 6923 "Expense User"
             CalcFormula = lookup(Employee.Status where("No." = field("Employee No.")));
             Editable = false;
         }
+        field(25; "Employee Posting Group"; Code[20])
+        {
+            Caption = 'Employee Posting Group';
+            ToolTip = 'Specifies the employee posting group of the related employee. Expenses cannot be posted without it.';
+            FieldClass = FlowField;
+            CalcFormula = lookup(Employee."Employee Posting Group" where("No." = field("Employee No.")));
+            Editable = false;
+        }
         field(23; "Approver No."; Code[20])
         {
             Caption = 'Approver No.';
@@ -227,6 +240,7 @@ table 6923 "Expense User"
         ExpenseApprovalSetupErr: Label 'You cannot remove approval rights from expense user %1. This expense user is currently configured as an approver in the %2.', Comment = '%1 - Expense User No., %2 - Table Caption';
         DuplicateEmailErr: Label '%1 %2 is already used by another %3. %1 must be unique.', Comment = '%1 = Email Caption, %2 = Email address, %3 = Expense User Table Caption';
         DuplicateEmployeeNoErr: Label '%1 %2 is already linked to another %3. Each employee can only be linked to one %3.', Comment = '%1 = Employee No. Caption, %2 = Employee No., %3 = Expense User Table Caption';
+        EmployeePostingGroupMissingErr: Label '%1 %2 cannot be linked to an %3 because %4 is not specified on the %1.', Comment = '%1 = Employee Table Caption, %2 = Employee No., %3 = Expense User Table Caption, %4 = Employee Posting Group Field Caption';
         OnlyBCUserCanApproveErr: Label 'In order to be an expense approver there must be a user in Business Central for email %1 for expense user %2.', Comment = '%1 - Email, %2 - Expense User No.';
         CannotDeleteExpenseUserWithExpenseErr: Label 'You cannot delete Expense User %1 because they have active expense.', Comment = '%1 = Expense User No.';
         CannotDeleteExpenseUserWithExpenseReportErr: Label 'You cannot delete Expense User %1 because they have active expense report.', Comment = '%1 = Expense User No.';
diff --git a/src/Apps/W1/ExpenseAgent/demo data/Country/CreateExpenseCountryData.Codeunit.al b/src/Apps/W1/ExpenseAgent/demo data/Country/CreateExpenseCountryData.Codeunit.al
index c6bed8083b5..89777dbc3c4 100644
--- a/src/Apps/W1/ExpenseAgent/demo data/Country/CreateExpenseCountryData.Codeunit.al	
+++ b/src/Apps/W1/ExpenseAgent/demo data/Country/CreateExpenseCountryData.Codeunit.al	
@@ -122,6 +122,9 @@ codeunit 8222 "Create Expense Country Data"
     begin
         CountryCode := GetCountryCode();
 
+        if CountryCode = 'ES' then
+            Codeunit.Run(Codeunit::"Update Employee ES");
+
         Codeunit.Run(Codeunit::"Create Expense Location");
         Codeunit.Run(Codeunit::"Create Expense Categories DM");
         Codeunit.Run(Codeunit::"Create Expense Subcategories");
@@ -130,12 +133,7 @@ codeunit 8222 "Create Expense Country Data"
         Codeunit.Run(Codeunit::"Create Expense User");
 
         case CountryCode of
-            'ES':
-                begin
-                    Codeunit.Run(Codeunit::"Update Employee ES");
-                    CreateCountryMasterData(CountryCode);
-                end;
-            'AT', 'AU', 'BE', 'CA', 'CH', 'CZ', 'DE', 'DK', 'FI', 'FR', 'GB', 'IT', 'NL', 'NO', 'NZ', 'US':
+            'AT', 'AU', 'BE', 'CA', 'CH', 'CZ', 'DE', 'DK', 'ES', 'FI', 'FR', 'GB', 'IT', 'NL', 'NO', 'NZ', 'US':
                 CreateCountryMasterData(CountryCode);
         end;
     end;
diff --git a/src/Apps/W1/ExpenseAgent/test/src/ExpenseTestII.Codeunit.al b/src/Apps/W1/ExpenseAgent/test/src/ExpenseTestII.Codeunit.al
index 722114c2da5..f19f8e90668 100644
--- a/src/Apps/W1/ExpenseAgent/test/src/ExpenseTestII.Codeunit.al
+++ b/src/Apps/W1/ExpenseAgent/test/src/ExpenseTestII.Codeunit.al
@@ -36,6 +36,7 @@ codeunit 148309 "Expense Test II"
         LibraryVariableStorage: Codeunit "Library - Variable Storage";
         LibraryNotificationMgt: Codeunit "Library - Notification Mgt.";
         LibraryTemplates: Codeunit "Library - Templates";
+        LibraryHumanResource: Codeunit "Library - Human Resource";
         NotificationLifecycleMgt: Codeunit "Notification Lifecycle Mgt.";
         IsInitialized: Boolean;
         AddExpenseTo: Option "New Expense Report","Existing Expense Report";
@@ -59,6 +60,7 @@ codeunit 148309 "Expense Test II"
         CannotDeleteEmployeeWithExpenseReportErr: Label 'You cannot delete Employee %1 because they have active expense report.', Comment = '%1 = Employee No.';
         CannotDeleteEmployeeWithExpenseErr: Label 'You cannot delete Employee %1 because they have active expense.', Comment = '%1 = Employee No.';
         CannotDeletePaymentMethodInUseErr: Label 'You cannot delete %1 %2 because it is used as the %3 for %4 %5.', Comment = '%1 = Table Caption, %2 = Payment Method Code, %3 = Default Payment Method Field Caption, %4 = Expense Category Table Caption, %5 = Expense Category Code';
+        EmployeePostingGroupMissingErr: Label '%1 %2 cannot be linked to an %3 because %4 is not specified on the %1.', Comment = '%1 = Employee Table Caption, %2 = Employee No., %3 = Expense User Table Caption, %4 = Employee Posting Group Field Caption';
 
     [Test]
     procedure ExpenseDetailRequiredMustFlowToExpenseFromExpenseCategory()
@@ -3115,6 +3117,67 @@ codeunit 148309 "Expense Test II"
         Assert.ExpectedError(StrSubstNo(BillableCustomerAndProjectErr, Expense.FieldCaption("Billable to Customer"), Expense.FieldCaption("Job No.")));
     end;
 
+    [Test]
+    procedure ExpenseUserCannotBeLinkedToEmployeeWithoutPostingGroup()
+    var
+        Employee: Record Employee;
+        ExpenseUser: Record "Expense User";
+    begin
+        // [FEATURE] [AI TEST]
+        // [SCENARIO 645043] Verify that an Expense User cannot be linked to an Employee without an Employee Posting Group.
+        Initialize();
+
+        // [GIVEN] An Employee "E" without an Employee Posting Group.
+        LibraryHumanResource.CreateEmployee(Employee);
+        Employee.Validate("Employee Posting Group", '');
+        Employee.Modify(true);
+
+        // [WHEN] Link Employee "E" to a new Expense User "U".
+        ExpenseUser.Init();
+        ExpenseUser.Validate("No.", LibraryUtility.GenerateRandomCode(ExpenseUser.FieldNo("No."), Database::"Expense User"));
+        asserterror ExpenseUser.Validate("Employee No.", Employee."No.");
+
+        // [THEN] An error is thrown stating that the Employee Posting Group is not specified on the Employee.
+        Assert.ExpectedError(
+            StrSubstNo(
+                EmployeePostingGroupMissingErr, Employee.TableCaption(), Employee."No.",
+                ExpenseUser.TableCaption(), Employee.FieldCaption("Employee Posting Group")));
+        Assert.ExpectedErrorCode('Dialog');
+    end;
+
+    [Test]
+    procedure ExpenseUserCanBeLinkedToEmployeeWithPostingGroup()
+    var
+        Employee: Record Employee;
+        ExpenseUser: Record "Expense User";
+    begin
+        // [FEATURE] [AI TEST]
+        // [SCENARIO 645043] Verify that an Expense User can be linked to an Employee with an Employee Posting Group.
+        Initialize();
+
+        // [GIVEN] An Employee "E" with an Employee Posting Group.
+        LibraryHumanResource.CreateEmployee(Employee);
+
+        // [WHEN] Link Employee "E" to a new Expense User "U".
+        ExpenseUser.Init();
+        ExpenseUser.Validate("No.", LibraryUtility.GenerateRandomCode(ExpenseUser.FieldNo("No."), Database::"Expense User"));
+        ExpenseUser.Validate("Employee No.", Employee."No.");
+        ExpenseUser.Insert(true);
+
+        // [THEN] Expense User "U" is linked to Employee "E" and shows the Employee Posting Group of "E".
+        ExpenseUser.CalcFields("Employee Posting Group");
+        Assert.AreEqual(
+            Employee."No.",
+            ExpenseUser."Employee No.",
+            StrSubstNo(ValueMustBeEqualErr, ExpenseUser.FieldCaption("Employee No."), Employee."No.", ExpenseUser.TableCaption()));
+        Assert.AreEqual(
+            Employee."Employee Posting Group",
+            ExpenseUser."Employee Posting Group",
+            StrSubstNo(
+                ValueMustBeEqualErr, ExpenseUser.FieldCaption("Employee Posting Group"),
+                Employee."Employee Posting Group", ExpenseUser.TableCaption()));
+    end;
+
     local procedure Initialize()
     var
         Workflow: Record Workflow;