By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. A 10 day payoff is crucial to getting your old loans paid off during a refinance.Learn how it works from start to finish. Please include a per diem amount in the statement. Please email this information to as soon as possible. Discover more about per diem interest—the daily interest on a loan that occurs outside of the standard repayment period.