We debited an acct owned by John Doe at bank A by ACH. Funds received and we cut a check to pay bank B. 30 days later Doe says the authorization to debit was revoked.Tells his bank so that bank says, give us back the money. At this point can we request proof of this authorization, i.e. can we ask for a copy of it, seeing as how we are out the money...?

If you debited the account, wouldn't you be the one required to have the authorization for that debit? And if you were authorized to do the transaction, you should just supply them proof of that authorization and you are not out the money.

I was dealing with revoked authorizations...I learned that NACHA provides for obtaining a copy of the revocation if we ask for it.