A method for validating an electronic payment by a credit/debit card in a transaction system. The method includes registering a purchase of an article by a buyer using a credit/debit card associated with at least one PIN code, checking that the at least one PIN code is associated with the number of said credit/debit card provided by said buyer to said seller terminal, checking, by said electronic payment center, whether or not said at least one PIN code is valid, and one of: after the at least one PIN code is found to be valid, checking, by said electronic payment center, whether the electronic payment center has received a pre-validation from a third party; after the at least one PIN code is found to be valid, contacting a third party via a communication network and requesting that the third party validate the purchase; and after the at least one PIN code is found to be valid, contacting a third party via a communication network and requesting said at least one PIN code from the third party. The third party is a prime owner of the credit/debit card.