I have a customer that claims he never signed any papers to be a co-signer on his sons loan with another financial institution. My questions is where do we go from here? What are we as a financial institution required to do and in what time frame? I should note we really do not believe the customer as he has fabricated things about his life before, however not about his financial life so it is raising a red flag.

I think that you just need to point them in the direction of the credit bureaus and that financial institution. You don't have a dog in the fight in this scenario.