I am not very familiar with NACHA. A customer purchased something in e-bay using his checking account number and routing number. He never received the product he purchased. Can he request the bank try to get his money back based on this information? Are there any rules/procedures we need to follow? I am aware of a form for unauthorized or improper ACH debits, but this would not apply. Thanks for any help you can give me.

Because the customer did, in fact, authorize this transaction, his dispute is going to be with the seller, not the bank. His best bet is going to be to contact the seller and ebay to try to get this resolved.

Are you sure it was an ACH transaction? I haven't been on ebay for awhile (got addicted. you know how it goes) but the only way I can think of to pay them electronically by any means is through using services such as paypal. You can be debited by Paypal one of two ways (that I know of. I could be wrong) by direct ACH out of your account after being confirmed or by using your debit card.
If the buyer was confirmed and did the transaction as an ACH, 'A' is right, there really isn't much to go on. However, if the transaction was used as a debit card (the quick and easy way IMO) then you could attempt to complete a dispute through Visa (or whomever).

Just a thought. I'm assuming of course...could be all sorts of wrong.

It was not paid with a debit/credit card. Aparently the seller would not accept it that way.

Apparantly the seller knows what he's doing.

Yeah, I can't think of a legitimate way you could return an ACH in this situation either. He did authorize the transaction.