Money & WorkFact
A "card payment fee" is void for the usual cards.
Section 270a of the German Civil Code voids any agreement charging you extra for a SEPA credit transfer, SEPA direct debit or a common consumer payment card. It implements the EU Payment Services Directive. For other routes, such as some commercial cards, a surcharge can still be lawful.
Useful: If a "card fee" appears at checkout, check which payment method it actually refers to.
Source: dejure.org