In any proceeding before an appeal tribunal involving an appeal from a disputed order and notice of assessment (for contributions, interest, or penalties due) a disputed denial of refund or adjustment (of contributions, interest, or penalties paid) or a disputed experience rating credit, the appeal tribunal, after affording the parties a reasonable opportunity for hearing, shall affirm, modify or set aside the notice of assessment, denial of refund or experience rating credit. The parties shall be duly notified of such appeal tribunal's decision together with its reasons therefor which shall be deemed to be the final decision on the order and notice of assessment, denial of refund or experience rating credit, as the case may be, unless within thirty days after the date of notification or mailing, whichever is the earlier, of such decision, further appeal is perfected pursuant to the provisions of this title relating to review by the commissioner.