Labor and Industries
Motor Vehicle Collisions
Personal Injury Protection Plans and 3rd Party Billing
Classes from Adler Giersh Attorneys
Massage Insurance Billing Manual
I have written the 4th edition of my book on Insurance Billing. While it is not specific to WA State, it will help you to understand the process of billing and learn to ask what questions to what parties in order to bill and get paid.
It is available in PDF, Kindle and Paperback through my other website www.massagepracticebuilder.com