By including a per diem amount in the letter, the parties will not have to execute another payoff letter if the termination date. The first step is to get in touch with your lender or loan servicer.You can find their contact information on your monthly statements. It typically details the principal balance, interest due as of that date, per diem, any late fees, etc. Discover more about per diem interest—the daily interest on a loan that occurs outside of the standard repayment period. Typically, a 10day payoff letter includes: The 10day payoff date and payoff quote for your loan. Your loan account number(s) The new interest calculation applies when an FHA loan with a Note date of January 21, 2015 or after, is paid in full. Per diem is an allowance for lodging, meals, and incidental expenses. The US General Services Administration (GSA) establishes the per diem reimbursement rates.