diff --git a/counter/models.py b/counter/models.py
index 9fade666..2ac691e0 100644
--- a/counter/models.py
+++ b/counter/models.py
@@ -52,7 +52,8 @@ class CustomerQuerySet(models.QuerySet):
     def update_amount(self) -> int:
         """Update the amount of all customers selected by this queryset.
 
-        The result is given as the sum of all refills minus the sum of all purchases.
+        The result is given as the sum of all refills
+        minus the sum of all purchases paid with the AE account.
 
         Returns:
             The number of updated rows.
@@ -73,7 +74,9 @@ class CustomerQuerySet(models.QuerySet):
             .values("res")
         )
         money_out = Subquery(
-            Selling.objects.filter(customer=OuterRef("pk"))
+            Selling.objects.filter(
+                customer=OuterRef("pk"), payment_method="SITH_ACCOUNT"
+            )
             .values("customer_id")
             .annotate(res=Sum(F("unit_price") * F("quantity"), default=0))
             .values("res")
diff --git a/counter/tests/test_customer.py b/counter/tests/test_customer.py
index 7153142d..bc3f4fb4 100644
--- a/counter/tests/test_customer.py
+++ b/counter/tests/test_customer.py
@@ -442,6 +442,7 @@ def test_update_balance():
             _quantity=len(customers),
             unit_price=10,
             quantity=1,
+            payment_method="SITH_ACCOUNT",
             _save_related=True,
         ),
         *sale_recipe.prepare(
@@ -449,10 +450,26 @@ def test_update_balance():
             _quantity=3,
             unit_price=5,
             quantity=2,
+            payment_method="SITH_ACCOUNT",
             _save_related=True,
         ),
         sale_recipe.prepare(
-            customer=customers[4], quantity=1, unit_price=50, _save_related=True
+            customer=customers[4],
+            quantity=1,
+            unit_price=50,
+            payment_method="SITH_ACCOUNT",
+            _save_related=True,
+        ),
+        *sale_recipe.prepare(
+            # all customers also bought products without using their AE account.
+            # All purchases made with another mean than the AE account should
+            # be ignored when updating the account balance.
+            customer=iter(customers),
+            _quantity=len(customers),
+            unit_price=50,
+            quantity=1,
+            payment_method="CARD",
+            _save_related=True,
         ),
     ]
     Selling.objects.bulk_create(sales)