diff --git a/registripe/views.py b/registripe/views.py
index d5083fa0..8207e2b7 100644
--- a/registripe/views.py
+++ b/registripe/views.py
@@ -30,6 +30,13 @@ def pubkey_script(request):
 
 
 def card(request, invoice_id):
+    ''' View that shows and processes a Stripe CreditCardForm to pay the given
+    invoice. Redirects back to the invoice once the invoice is fully paid.
+
+    Arguments:
+        invoice_id (castable to str): The invoice id for the invoice to pay.
+
+    '''
 
     form = forms.CreditCardForm(request.POST or None)
 
@@ -40,6 +47,9 @@ def card(request, invoice_id):
 
     to_invoice = redirect("invoice", inv.invoice.id)
 
+    if inv.invoice.balance_due() <= 0:
+        return to_invoice
+
     if request.POST and form.is_valid():
         try:
             inv.validate_allowed_to_pay()  # Verify that we're allowed to do this.