By law, most sellers of real property must provide a completed Seller Disclosure Statement (aka Form 17) to any buyer. You must fill out a Seller Disclosure Statement (also known as Form 17).You must tell the buyer any problems with the property that you know about. 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! Hey Buddy Buck here! The seller disclosure statement, also known as a seller disclosure form or Form17 is a crucial document that sellers must complete when selling their home. Nearly all real estate sales in Washington State require a seller disclosure statement, also known as Form 17, to be given to the buyer. For your protection you must date and sign each page of this disclosure statement and each attachment. This document MUST be completely filled out.