By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. Please accept this as my authorization to issue a payoff statement to.Through an effective date of . It typically details the principal balance, interest due as of that date, per diem, any late fees, etc. What is a Payoff Agreement? A payoff agreement is an informal contract in which a creditor agrees to accept the balance of a debt owed as full payment. A mortgage payoff letter can come in two forms. One form tells borrowers the remaining principal amount and interest they have to pay to close out the loan.