In looking through the DMV website for Tennessee, it does not appear that you need a bill of sale in order to register the used car.  Your transaction is know as a "private party purchase" meaning that you did not get the car from a dealer.  It is my understanding that a private party purchase situation you only need the following:Properly assigned title. Odometer Disclosure Statement. Your current registration (only required if you're transferring your plate).Although having a bill of sale is always a good idea - everything in writing as well, even the representations - you need not be held hostage here. Do not let him bully you in any way.  You have already paid dearly.  Now what you want to do about that is another question entirely. Good luck.