a method of arranging for payment of a purchase includes receiving , from a supplier , agreement to accept a payment from a buyer via use of a payment card having variable payment terms ; after a purchase by the buyer from the supplier , assessing the supplier a standard interchange rate ; receiving , from the buyer , approval to pay the invoice ; and issuing , to the supplier , a rebate , based upon when the approval to pay the invoice was received . the variable payment terms are calculated by : determining a first early payment date ; determining a second standard payment date ; assessing against the supplier a first percentage of the standard interchange rate if the invoice is approved by the first early payment date ; and assessing against the supplier a second percentage of the standard interchange rate if the invoice is approved on or after the second standard payment date .