If your debit-card swipe fees don’t go down after Oct. 1, 2011, you’re paying too much. That’s what Bob Baldwin, president of Heartland Payment Systems, Princeton, NJ, has been telling his customers in recent months. Baldwin’s comments come in the wake of the implementation of the Durbin Amendment, which passed as part of the Dodd-Frank financial reform bill.

A mouthful, the Durbin amendment simply lowers the amount card brands—Visa, MasterCard, Discover—can charge for each debit card transaction. That, in turn, lowers the fees issuing banks collect from a hotel each time a consumer uses the debit card.

It doesn’t, however, mean card processors have to pass that change to their clients, in this case, your hotel. So, you may not see the change unless you ask for it.

(Note: These changes are limited to debit cards, not credit cards.)

To better understand, consider that currently interchange or swipe fees range between 1.5% to 2.5% for each card-based purchase. When the amendment goes into action in October, banks can only collect 21 cents per transaction, plus 0.05% of the volume of transaction.

This new structure is pennies per transaction driven, not percentage of the sale driven. Still, it will save thousands for most hotels.

Baldwin uses an example of an average hotel room rate of $142. Pre-Durbin reform the swipe fee would have been $1.59. Post Durbin the rate is only 29 cents. That comes from the 21 cent fee, plus 0.05% of the $142 room rate.

A little story problem shows the significance to a hotel. Assume you sell 10 rooms everyday for one year at an ADR of $142. Assume all those guests pay with debit cards. That’s means you’ll pay 20 percent of your previous fees, or $1,060 instead of $5,800.

These numbers, of course, change with the size of the transaction and the number of rooms sold. They can mean big money to a big property … if they take advantage of the law change.

“How much you’ll save depends on the deal you have with your card processor,” explains Baldwin. “Heartland has taken the stance that the reduction should be passed through to the merchant.