Under my endorsement, exactly what do I write on the back of the refund check that I want to cash, but disputing the amount?

1. If it says "payment in full" on the front or back or any accompanying paper, or there is any other indication it is being tendered as full payment, do not cash or deposit it unless you are willing to forego any other rights. 2. To be safe, if you seriously intend to pursue the sender for more money, you should notify the sender in writing prior to depositing or cashing the check that you think you are entitled to more and will deposit it on x date as part payment. Wait the specified time before depositing.