Again, if this is a late return, you are not required to do anything. The typical hold harmless letters I have seen state something to the effect of ...
"In consideration of the payment by ?????? (Bank Name) (“Depository”) in the amount of up to $????????? to the undersigned ..."
If you wanted to cooperate you could send the amount that is left in the account. You do not need to, nor should you, send the entire amount; that would create a loss to your
bank. Please check with your legal counsel / operations management to get their take on the situation.
If this is not a late return and they have notified you of the forgery within the midnight deadline, your bank will be on the hook to collect from your customer.
I am by no means a legal expert on the matter...just someone who has dealt with it on occasion. Hopefully one of the experts in this forum will chime in soon.
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Opinions expressed may not be those of my employer.