A 10day payoff refers to the time it takes for your new lender to pay off your old loans during a refinance. It's the payoff amount 10 days in the future.A payoff letter provides instructions on how to pay off a loan with a lump sum before the loan term ends. Learn how payoff letters work. The first step is to get in touch with your lender or loan servicer. You can find their contact information on your monthly statements. A dealership will require a 10day payoff when you trade a vehicle to allow time to complete the paperwork and get the payoff funds to the lender. Discover more about per diem interest—the daily interest on a loan that occurs outside of the standard repayment period. By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date.