John customer pays Joe non-customer with a check drawn on customer's account with us. Non comes in anc cashes the check. Walks out the door. Non calls and says wife was supposed to make a copy of the check for their files and forgot. Calls bank and asks for a copy of check.

Can we give a copy of the check once negociated? I thought we should get permission from our cust. before providing a copy. What say you?

They could have taken a copy before they cashed it so I don't see why you wouldn't be able to give a copy to them now, except if maybe they weren't really the ones the check was payable to.

IMO I would have non-customer contact the person who wrote him/her the check and see if they could get a copy for them. No privacy issues to deal with then.