Wash. Rev. Code § 50.12.140
The commissioner may destroy any form, claim, ledger, check, letter, or other record of the employment security department at the expiration of three years after such record was originated by or filed with the employment security department, except that warrants and claims, claim determination, employer liability forms and contribution reports may be destroyed at the expiration of six years after such form is originated by or filed with the employment security department, and except that this section shall not apply to records pertaining to grants, accounts or expenditures for administration, records of the unemployment compensation fund and the unemployment compensation administration fund.
RCW 50.12.140
Preservation and destruction of public records: Chapter 40.14 RCW.