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.By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. 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. (each as defined in the Payoff Letter) have been paid in full in cash. Per year, one service per day is not applicable for recipients who are from birth up to the age of 21.