020) since January 1, 1995. Washington law says that when you sell your home, you must fill out a Seller Disclosure Statement (also known as Form 17).Nearly all real estate sales in Washington State require a seller disclosure statement, also known as Form 17, to be given to the buyer. Am a RE broker in SEA. This document MUST be completely filled out. Deliver to the buyer a completed seller disclosure statement in the following format and that contains, at a minimum, the following information. Learn more about the NWMLS Form 17 (or Seller Disclosure Statement). Almost all sellers in WA must complete and provide one to a buyer. The Seller Disclosure Statement (SDS - Form 17 for residential 1-4 unit properties or 17C for land zoned residential) is NOT referenced in the PSA. The. Completing the form is essential since it tells most about the condition of the property before the purchase is made.