update detail.

API/ROLAC.API/Entities/Expense.cs

@@ -5,12 +5,9 @@ public class Expense : SoftDeleteEntity, IAuditable
 {
     public int      Id              { get; set; }
     public int      MinistryId      { get; set; }
-    public int      CategoryGroupId { get; set; }
-    public int      SubCategoryId   { get; set; }
     public string   Type            { get; set; } = "StaffReimbursement"; // VendorPayment | StaffReimbursement
     public string   Status          { get; set; } = "Draft";             // see state machine
-    public string?  FunctionalClass { get; set; }   // null = inherit Ministry.DefaultFunctionalClass
-    public decimal  Amount          { get; set; }
+    public decimal  Amount          { get; set; }   // denormalized total = SUM(Lines.Amount), recomputed server-side
     public string   Description     { get; set; } = null!;
     public string?  VendorName      { get; set; }
     public int?     MemberId        { get; set; }
@@ -26,8 +23,7 @@ public class Expense : SoftDeleteEntity, IAuditable
     public DateTimeOffset? PaidAt      { get; set; }
     public string?        PaidBy      { get; set; }
 
-    public Ministry?             Ministry      { get; set; }
-    public ExpenseCategoryGroup? CategoryGroup { get; set; }
-    public ExpenseSubCategory?   SubCategory   { get; set; }
-    public Member?               Member        { get; set; }
+    public Ministry?         Ministry { get; set; }
+    public Member?           Member   { get; set; }
+    public List<ExpenseLine> Lines    { get; set; } = new();
 }

API/ROLAC.API/Entities/ExpenseLine.cs

@@ -0,0 +1,23 @@
+using ROLAC.API.Entities.Base;
+namespace ROLAC.API.Entities;
+
+/// <summary>
+/// One category line of an <see cref="Expense"/>. A single invoice/payment can span
+/// multiple expense categories, so the category / amount / functional-class axis lives
+/// here per line; the Expense header keeps payment-level info and a denormalized total.
+/// Lines are wholly owned by the header (replaced as a set on update, like CheckLine).
+/// </summary>
+public class ExpenseLine : AuditableEntity
+{
+    public int      Id              { get; set; }
+    public int      ExpenseId       { get; set; }
+    public int      CategoryGroupId { get; set; }
+    public int      SubCategoryId   { get; set; }
+    public string?  FunctionalClass { get; set; }   // null = inherit Ministry.DefaultFunctionalClass
+    public decimal  Amount          { get; set; }
+    public string?  Description     { get; set; }    // optional per-line note (header description is authoritative for check printing)
+
+    public Expense?              Expense       { get; set; }
+    public ExpenseCategoryGroup? CategoryGroup { get; set; }
+    public ExpenseSubCategory?   SubCategory   { get; set; }
+}

API/ROLAC.API/Entities/FunctionalClasses.cs

@@ -2,7 +2,7 @@ namespace ROLAC.API.Entities;
 
 /// <summary>
 /// The three IRS Form 990 Part IX functional-expense columns. Stored verbatim in
-/// Ministry.DefaultFunctionalClass and Expense.FunctionalClass.
+/// Ministry.DefaultFunctionalClass and ExpenseLine.FunctionalClass.
 /// </summary>
 public static class FunctionalClasses
 {