Admission of additional evidence limited to specified exceptions, with written reasons and opportunity to rebut required. Admission of additional evidence before the Commissioner (Appeals) is limited to four exceptions: refusal by the adjudicating authority to admit evidence that ought to have been admitted; prevention for sufficient cause from producing evidence when called upon; prevention for sufficient cause from producing evidence relevant to a ground of appeal; and adjudication without sufficient opportunity to adduce relevant evidence. The Commissioner (Appeals) must record written reasons for admitting such evidence and must allow the adjudicating authority a reasonable opportunity to examine, cross examine, or rebut the evidence; the Commissioner (Appeals) also may direct production of documents or witnesses to decide the appeal.