1. A payment device, comprising an input unit ( 2 ) arranged to receive first data taken from a medium ( 1 ) and identifying a user who will proceed with a payment for a purchase which he has made, said input unit being arranged to be connected to a first terminal ( 4 ) intended to be placed in a point of sale, said first terminal having a data input ( 5 ) intended to receive second data concerning said purchase, said first terminal being arranged to communicate the first and second data to a second terminal ( 8 ) intended to be placed with a financial body which will be responsible for making the payment on behalf of the user, said device also comprising a third terminal ( 9 ) intended to be placed at a payment management center, said third terminal ( 9 ) being arranged to manage the communication between the first ( 4 ) and second ( 8 ) terminals, said third terminal ( 9 ) having a first calculation unit ( 10 ) arranged to process payments in cash and a second calculation unit ( 11 ) arranged to process payments in compensatory value from a non-financial credit accumulated by the user, said input unit ( 2 ) being provided with selection means ( 3 ) for indicating either a payment mode in cash or a payment mode in compensatory value and to produce a first control signal if the payment mode in cash is selected and a second control signal if the compensatory value mode is chosen, said third terminal ( 9 ) also being arranged to receive the first and second control signals and to execute the payment under the control of the second control signal and to transmit the first and second data to the second terminal ( 8 ) under the control of the first control signal.