(1) An interested party is entitled to receive notice of Board of Labor Appeals proceedings as well as a copy of the board's decision. An interested party will be given an opportunity to participate in the board's hearing on the appeal.

(a) A claimant is an interested party in an appeal of the claimant's benefits determination decision.

(b) An employer is an interested party to an appeal that is determinative of whether benefits paid to a claimant are chargeable to that employer's account.

(c) An employer is an interested party to an appeal of decision on contribution, liability, contribution rate, application for refund, subject wages, self-employment, or other contribution related issues.

(d) The department is an interested party.

(e) Any party who, upon written application to the board, is found to have a substantial interest in an issue may be deemed to be an interested party relative to the appeal.