A Satisfaction of Security Instrument is a document that shows an individual has paid a deed of trust or a mortgage in full. A 10day payoff refers to the time it takes for your new lender to pay off your old loans during a refinance.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. Depending on your lender, you may have to sign in to an online account, call a helpline, or send a formal letter to start the request process. There's probably an online form. Always write the account number(s) you wish to pay in the memo section on your check. If making an advance payment, also write 'Prepayment' in this area. We offer a complete array of financial services for our membership. We work to provide products and services you need at a great value with great service.