[wiredfool]

Actually, there is. If you're doing ACH, you need an authorization, in one of several forms depending on the circumstances. The bank doesn't check the authorization unless there's a significant issue, but they have a right to demand it. I've only seen it happen when there's been a bunch of fraud going on.

You can reverse ACH transactions by going to your bank and filling about a form and making a declaration under penalty of perjury. It goes back to the merchant as an R10, and the merchant usually deals with it in some other form, though if they've got a good relationship with their bank, they can dishonor the return.