This link points to the portion of the State Court web site where you will find the forms for declaring a marriage invalid.

The following forms are included at this web site:

WPF DR 01.0120     Petition for Declaration Concerning Validity (Marriage)
WPF DRPSCU 09.0200     Confidential Information Form (INFO)    
WPF DRPSCU 09.0210     Addendum to Confidential Information Form (AD)    
Case Information Cover Sheet (Case Types 3 – 6)
WPF DR 01.0200    
WPF DRPSCU 01.0250     Return of Service (RTS)    
WPF DRPSCU 01.0330     Joinder (JN)    
WPF DRPSCU 01.0310     Acceptance of Service (ACSR)      
WPF DR 01.0300     Response to Petition (Marriage) (RSP)    
WPF DR 04.0300     Findings of Fact and Conclusions of Law (Marriage) (FNFCL)    
WPF DR 04.0400     Decree of Dissolution (DCD)/Legal Separation (DCLGSP)/Concerning the Validity of the Marriage (DCINMG)    
WPF DR 04.0500     Restraining Order (TRO/RSTO)    
WPF DR 01.0500     Order of Child Support (TMORS, ORS)    
WSCSS - Schedule     Washington State Child Support Schedule Definitions and Standards, Instructions and Economic Table    
WSCSS - Worksheets     Washington State Child Support Schedule Worksheets (CSW)    
WPF DRPSCU 01.1550     Financial Declaration (FNDCLR)    
WPF DRPSCU 09.0220     Sealed Financial Source Documents (Cover Sheet) (SEALFN)    
WPF DR 01.0400     Parenting Plan; Proposed (PPP), Temporary (PPT), Final Order (PP)
WPF DR 01.0410     Residential Time Summary Report (RTSR)