What to expect, when to discharge your mortgage, how much it costs and where to get more information. For existing Suffolk Building Society mortgage borrowers who may have problems paying their mortgage we are here to help.Download application forms for accounts and services, get information about credit union fees and more from Suffolk Credit Union in NY. Explore online. If you're an existing borrower with a Suffolk Building Society mortgage find out how to manage your mortgage, borrow more, change your deal and get support. 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. Also at issue is whether a HUD-1 closing statement can be treated as conclusive proof of the mortgage.