Actually, PPD transactions can be subject to stop payments under NACHA rules if the stop order is received soon enough for the bank to act on the order.
The 3-day advance notice requirement found in Reg. E (and, interestingly, in NACHA rules too) mandates the acceptance of a stop order with the advance notice. NACHA rules make it clear that you have the OPTION to accept a stop order later than that, if you can return the item within your return item deadline.
As you've gathered, the payday loan company can submit another debit unless your customer revokes her authorization for them to debit the account.
If you customer challenges a PPD to the payday lender after the fact (too late for a stop), alleging non-authorization, you have to open the case, make your decision (I assume it will be that the customer authorized the EFT), issue your determination and move on. Part of moving on may well be to sever your deposit relationship with this individual.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8