Domestic Partnership Law took effect  Thursday, June 12, 2008.  This law does not create a legal relationship that is equivalent to marriage, but does create property rights that previously applied only to married persons.

Who can enter into a Domestic Partnership?
Two people of the same sex of any age over 18 and capable of consent.
Two people of the opposite sex, at least one of whom is over 62 years of age.

Domestic Partnerships are established in Washington by simply filing with the Washington Secretary of State’s Office.

useful links:
DomesticPartnerships
Frequently Asked Questions
Domestic Partnership Declaration.pdf

When you take title of real property in the State of Washington as a domestic partnership, you will need these two forms...

Confidential Information Statement.pdf
Automatic Homestead.pdf

Seattle City Clerk’s Office…
The City of Seattle's Domestic Partnership Registration program allows unmarried couples in committed, on-going family relationships to document their relationships. Couples may consist of a man and a woman, two men, or two women.

Domestic Partnership Registration is voluntary, and does not create any new or different legal rights or responsibilities, or any contractual relationships or obligations between those registered.
http://www.seattle.gov/leg/clerk/dpr.htm

Washington State Legislature
Expanding rights and responsibilities for domestic partnerships.
HB 3104 updates...