Something else that Durbin did not address is what will happen to the interchange fee when a purchase is returned by a customer.

FORBES: Digesting The Impending Durbin-related Doom

The IRS considers deposits returned on termination of a purchase agreement.

FORBES: Contract Cancellations Trigger Taxes

Merchants issue a refund in an amount equaling the full purchase price when an item is returned, but the retailer may be taking a loss on such transactions because card processing fees are not refunded when transactions are reversed.

FORBES: Digesting The Impending Durbin-related Doom