The financial institution will most likely cash the check and temporarily credit your account for the amount of the check. Most scammer checks are fraudulent, and when the financial institution discovers this fraud, they have the right to demand full payment of the defrauded amount from the account holder. If you deposit a scammer's fraudulent check, you will be held responsible for repaying the full amount of the check. Another possible scenario is if the scammer's check is good. Here the scammer will almost always direct you to forward most of the amount to a third party while keeping a small percentage for your trouble. In this case, you unknowingly helped launder money by processing it through your account and now most likely need to answer law enforcement regarding possible criminal involvement.