In the beginning, the cashier pressed a special "food-stamp total" key, and the customer presented paper food stamps; today, the customer swipes an Electronic Benefit Transfer (EBT) card and selects the "food stamp" account, and the register charges only the food-stamp total to the EBT card.
IIAS does have one additional requirement that is not normally found with food stamps, though the U.S. Department of Agriculture can audit retailers directly for similar purposes: Beginning January 1, 2007, the merchant must make a record of each transaction available to the employer, or more commonly, to the employer's FSA or HRA provider.
This can be done contemporaneously with the transaction, or it may be provided later if the Internal Revenue Service ever audits the employer.
Though IIAS was first used in 2005, it was not officially approved by the Internal Revenue Service until July 2006, in IRS Notice 2006–69.
Because of this ruling, by 2009 most grocers, discounters, and chain or Internet pharmacies in the U.S. must have an IIAS in place in order to accept FSA debit cards.