Method for validating an electronic payment by a credit card in a transaction system comprising a seller terminal (12) for registering a sale of one or several articles by a buyer (10 or 11) using a credit card associated with a plurality of PIN codes and an electronic payment center (14) connected to the seller terminal by the Internet network (16). The method consists for the electronic payment center to check that a buyer PIN code which is provided by the buyer to the center is associated with the number of the credit card provided by the buyer to the seller terminal and is characterized in that it comprises a step automatically carried out by the electronic payment center of checking with a third party whether the buyer PIN code is valid.