Learn more about the NWMLS Form 17 (or Seller Disclosure Statement). Almost all sellers in WA must complete and provide one to a buyer.I'm going to show you how to send the form 17 to your sellers have them be able to fill out all of the boxes get it back and then be able to deliver it. The Seller Disclosure Statement in Washington (aka Form 17) is a mandatory form all sellers must complete and give to their buyers. Complete this application to obtain your sales tax Certificate of. Authority, which allows you to collect tax, make taxable sales in New. The Form 17 permits a seller to mark answers to the form questions as "Yes", "No", "I don't know", and "NA." 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! 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.