diff --git a/src/allmende_payment_system/api/shop.py b/src/allmende_payment_system/api/shop.py
index de5b6a0..4c4eaec 100644
--- a/src/allmende_payment_system/api/shop.py
+++ b/src/allmende_payment_system/api/shop.py
@@ -1,6 +1,7 @@
 from decimal import Decimal
+from typing import Annotated
 
-from fastapi import APIRouter, HTTPException, Request
+from fastapi import APIRouter, Form, HTTPException, Request
 from sqlalchemy import select
 from starlette import status
 from starlette.responses import RedirectResponse
@@ -29,17 +30,32 @@ async def get_cart(request: Request, session: SessionDep, user: UserDep):
 
     return templates.TemplateResponse(
         "order.html.jinja",
-        context={"request": request, "order": user.shopping_cart, "is_cart": True},
+        context={
+            "request": request,
+            "user": user,
+            "order": user.shopping_cart,
+            "is_cart": True,
+        },
     )
 
 
-@shop_router.get("/shop/finalize_order")
-async def finalize_order(request: Request, session: SessionDep, user: UserDep):
+@shop_router.post("/shop/finalize_order")
+async def finalize_order(
+    request: Request,
+    session: SessionDep,
+    user: UserDep,
+    account_id: Annotated[float, Form()],
+):
 
     cart = user.shopping_cart
 
-    # TODO: Implement
-    cart.finalize(user.accounts[0])
+    for account in user.accounts:
+        if account.id == account_id:
+            break
+    else:
+        raise HTTPException(status_code=400, detail="Invalid account ID.")
+
+    cart.finalize(account)
 
     return RedirectResponse(url=f"/", status_code=status.HTTP_302_FOUND)
 
diff --git a/src/allmende_payment_system/templates/order.html.jinja b/src/allmende_payment_system/templates/order.html.jinja
index 1f2422c..e24564e 100644
--- a/src/allmende_payment_system/templates/order.html.jinja
+++ b/src/allmende_payment_system/templates/order.html.jinja
@@ -70,8 +70,20 @@
 
         {% if is_cart %}
         <div class="d-flex justify-content-between align-items-center mt-3">
-            <div>
-                <a href="/shop/finalize_order" class="btn btn-primary">Jetzt Buchen</a>
+            <div    >
+                <form method="post" action="/shop/finalize_order" class="d-flex align-items-center">
+                    {% if user.accounts|length > 1 %}
+                        <select name="account_id" class="form-select form-select-sm me-2" required>
+                            <option value="">-- Konto wählen --</option>
+                            {% for account in user.accounts %}
+                                <option value="{{ account.id }}">{{ account.name }} ({{ account.balance | format_number }} €)</option>
+                            {% endfor %}
+                        </select>
+                    {% elif user.accounts|length == 1 %}
+                        <input type="hidden" name="account_id" value="{{ user.accounts[0].id }}">
+                    {% endif %}
+                    <button type="submit" class="btn btn-primary">Jetzt Bezahlen</button>
+                </form>
             </div>
         </div>
         {% endif %}
diff --git a/test/test_shop.py b/test/test_shop.py
index 8682093..d695255 100644
--- a/test/test_shop.py
+++ b/test/test_shop.py
@@ -147,19 +147,30 @@ def test_remove_item_from_cart_wrong_user(client: APSTestClient, test_db, produc
 def test_finalize_order(client: APSTestClient, test_db, product):
 
     user = create_user_with_account(test_db, "test", balance=100.0)
+    second_account = Account(name=f"Another account")
+    second_account.transactions.append(
+        Transaction(total_amount=Decimal(50.0), type="deposit")
+    )
+    test_db.add(second_account)
+    user.accounts.append(second_account)
 
     user.shopping_cart.items.append(
         OrderItem(product=product, quantity=2, total_amount=product.price * 2)
     )
     test_db.flush()
 
-    response = client.get("/shop/finalize_order", follow_redirects=False)
+    response = client.post(
+        "/shop/finalize_order",
+        follow_redirects=False,
+        data={"account_id": second_account.id},
+    )
     assert response.status_code == 302
 
     assert len(user.shopping_cart.items) == 0
     assert len(user.orders) == 2  # shopping cart + finalized order
 
-    assert user.accounts[0].balance == Decimal(100.0) - (product.price * 2)
+    assert user.accounts[0].balance == Decimal(100.0)
+    assert user.accounts[1].balance == Decimal(50.0) - (product.price * 2)
 
 
 def test_view_order(client: APSTestClient, test_db, product):