Need to get in touch? Suffolk Credit Union in Long Island, NY makes it easy to contact us.Download application forms for accounts and services, get information about credit union fees and more from Suffolk Credit Union in NY. Explore online. The seller should advise its bank of the projected closing date and request a payoff letter. 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.