By law, most sellers of real property must provide a completed Seller Disclosure Statement (aka Form 17) to any buyer. Hey Buddy Buck here!Almost every home seller in WA must complete a Seller Disclosure Statement, aka the Form 17. Learn more, and get a copy you can use for free! Fill out all of this form and other papers you are attaching before you sign this form in front of a notary. Completion and review of the Seller Disclosure Statement, Form 17, happens (or should happen) in nearly every transaction. This document MUST be completely filled out. Every question must be answered, if applicable. The Seller Disclosure Statement in Washington (aka Form 17) is a mandatory form all sellers must complete and give to their buyers. Your county assessor may require you to wait to complete your application(s) until the federal income tax returns have been filed with the IRS.