By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. Works 1,000 hours in a fiscal year. •.Works 125 days in a fiscal year, if paid on a per diem basis. 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. A blank sample HB Letter 16 is included. After receiving recognition from the.