Say you have a mortgage and want to know exactly how much you'd need to pay to satisfy the loan. A mortgage payoff letter will tell you that magic number.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. Do you need a loan payoff request form? You should definitely keep the letter telling you that your loan was paid off in full. We'd also want you to keep at least the most current loan statement. For an official statement verifying your existing mortgage balance, monthly payments, and any late payments, please complete a 3rd Party Authorization form. The mortgage payoff calculator helps you find out. Your account number is provided with the loan details in the welcome letter that you receive in the mail after your new loan is funded.