Wash. Rev. Code § 62A.3-522
In addition to sending a notice of dishonor to the drawer of the check under RCW 62A.3-520, the person sending notice shall execute an affidavit certifying service of the notice by mail. The affidavit of service by mail must be attached to a copy of the notice of dishonor and must be substantially in the following form:
AFFIDAVIT OF SERVICE BY MAIL
I, . . . . . ., hereby certify that on the . . . . . . day of . . . . . ., 20. . ., a copy of the foregoing Notice was served on . . . . . . by mailing via the United States Postal Service, postage prepaid, at . . . . . ., Washington.
Dated:. . . . . . . . . . . . . . ..
(Signature)
The person enforcing the check shall retain the affidavit with the check but shall file a copy of the affidavit with the clerk of the court in which an action on the check is commenced.
RCW 62A.3-522
Recovery of attorneys' fees-Effective date-1993 c 229: See RCW 62A.11-111 and 62A.11-112.