Multiple secure transactions are provided through use of a method that uses customer one-time unique purchase order numbers (“Coupons”) generated by an algorithm that uses a permutated user key and a user insertion key as input variables. A user key (such as a Personal Identification Number, or “PIN”) is combined with a permutation variable that is correlated with a customer sequence number to create the permutated user key. A random number generator is used to generate the user insertion key correlated with the customer sequence number. The algorithm can insert the permutated user key into a user account number through use of the user insertion key. A Coupon is validated by confirming that it is contained in a set of money source Coupons generated by a money source using the user key and a random number generator that is synchronized with the random number used to generate Coupons. Once a Coupon is validated, the matching money source Coupon and all earlier generated money source Coupons are deleted from the set, and a new set is generated. If a preselected number of Coupons are not validated for a chosen entity, an invalid user account number will be set. Coupons can be used for credit card or bank card transactions, and they can be generated without changing fixed digits of traditional twenty digit account numbers.