Wash. Rev. Code § 35.13.470
(1) The legislative body of a county, city, or town planning under chapter 36.70A RCW and subject to the requirements of RCW 36.70A.215 may initiate an annexation process for unincorporated territory by adopting a resolution commencing negotiations for an interlocal agreement as provided in chapter 39.34 RCW between a county and any city or town within the county. The territory proposed for annexation must meet the following criteria:
(4) If an interlocal agreement under this section is used for a sales and use tax under RCW 82.14.415, the agreement under this section must address the following:
[ 2023 c 351 s 1; 2003 c 299 s 1.]