diff --git a/counter/models.py b/counter/models.py
index 72058ef6..23ceaaa5 100644
--- a/counter/models.py
+++ b/counter/models.py
@@ -1402,5 +1402,9 @@ class InvoiceCall(models.Model):
         verbose_name = _("Invoice call")
         verbose_name_plural = _("Invoice calls")
 
+    def save(self, *args, **kwargs):
+        self.month = self._meta.get_field("month").to_python(self.month)
+        super().save(*args, **kwargs)
+
     def __str__(self):
         return f"invoice call of {self.month} made by {self.club}"
diff --git a/counter/tests/test_invoices.py b/counter/tests/test_invoices.py
new file mode 100644
index 00000000..1aebca5f
--- /dev/null
+++ b/counter/tests/test_invoices.py
@@ -0,0 +1,33 @@
+from datetime import date
+
+import pytest
+from model_bakery import baker
+
+from club.models import Club
+from counter.models import InvoiceCall
+
+
+@pytest.mark.django_db
+def test_invoice_date_with_date():
+    club = baker.make(Club)
+    invoice = InvoiceCall.objects.create(club=club, month=date(2025, 10, 20))
+
+    assert not invoice.is_validated
+    assert str(invoice) == f"invoice call of {invoice.month} made by {club}"
+    assert invoice.month == date(2025, 10, 1)
+
+
+@pytest.mark.django_db
+def test_invoice_date_with_string():
+    club = baker.make(Club)
+    invoice = InvoiceCall.objects.create(club=club, month="2025-10")
+
+    assert invoice.month == date(2025, 10, 1)
+
+
+@pytest.mark.django_db
+def test_invoice_call_invalid_month_string():
+    club = baker.make(Club)
+
+    with pytest.raises(ValueError):
+        InvoiceCall.objects.create(club=club, month="2025-13")