PDFRCW 50A.50.010
Generally.
(1) Any aggrieved party may file an appeal from any determination or redetermination with the commissioner within thirty days after the date of notification or mailing, whichever is earlier, of such determination or redetermination to the party's last known address. If an appeal with respect to any determination is pending as of the date when a redetermination is issued, such appeal, unless withdrawn, shall be treated as an appeal from such redetermination.
(2) Any appeal from a determination of denial of benefits shall be deemed to be an appeal as to all weeks subsequent to the effective date of the denial for which benefits have already been denied. If no appeal is taken from any determination, or redetermination, within the time allowed by the provisions of this section for appeal, the determination or redetermination, as the case may be, shall be conclusively deemed to be correct except as provided in respect to reconsideration by the commissioner of any determination.