diff --git a/apps/api/v1/services/budget.service.ts b/apps/api/v1/services/budget.service.ts
index 9401fe2d..c4e36d37 100644
--- a/apps/api/v1/services/budget.service.ts
+++ b/apps/api/v1/services/budget.service.ts
@@ -199,3 +199,21 @@ export async function findBudgetsOfUser({
     },
   })
 }
+
+export async function createBudgetUser({
+  userId,
+  budgetId,
+  permission,
+}: {
+  userId: string
+  budgetId: string
+  permission: BudgetUserPermission
+}) {
+  return prisma.budgetUser.create({
+    data: {
+      userId,
+      budgetId,
+      permission,
+    },
+  })
+}