Your commercial customers have a window of time in which to verify the items paid against their accounts. It is unreasonable, in my opinion, to hold a business customer to a next-day standard of notification unless your deposit contract specifically says so and the customer has access to online banking that permits such a daily review.
It is critical that bankers understand that their ability to return an item via the ACH has no legal bearing on the contract between the bank and its deposit account customer. It's really not any different from the idea that a bank has a midnight deadline to return an unauthorized (signature forged) check, although its customer has from 14 to 30 days (or longer) after the statement reflecting the payment of the check is delivered to claim that the check was wrongfully paid.
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