A notice of appeal may be amended as a matter of right within thirty days from the date the notice of appeal was received by the board. Thereafter, a party may amend the notice of appeal upon agreement in writing by the other party or when granted by the board. Motions to amend the notice of appeal shall be freely granted and may be denied only upon a showing by the adverse party of unreasonable and unavoidable hardship. Motions to amend must comply with WAC 456-10-510 and 456-10-410.

Amendments to the notice of appeal shall not extend any applicable jurisdictional deadline for appeal to the board.