As per rule 46A of the Income Rules, 1962
1) The appellant shall not be entitled to produce before the Commissioner (Appeals) any evidence, whether oral or documentary, other than the evidence produced by him during the course of proceedings before the Assessing Officer except in the following circumstances, namely :
a) where the Assessing Officer has refused to admit evidence which ought to have been admitted; or
b) where the appellant was prevented by sufficient cause from producing the evidence which he was called upon to produce by the Assessing Officer ; or
c) where the appellant was prevented by sufficient cause from producing before the Assessing Officer any evidence which is relevant to any ground of appeal ; or
d) where the Assessing Officer has made the order appealed against without giving sufficient opportunity to the appellant to adduce evidence relevant to any ground of appeal.
2) No evidence shall be admitted under sub-rule(1) unless the Commissioner (Appeals) records in writing the reasons for its admission.
3) The Commissioner (Appeals) shall not take into account any evidence produced under sub-rule(1) unless the Assessing Officer has been allowed a reasonable opportunity-
a) to examine the evidence or document or to cross-examine the witness produced by the appellant, or
b) to produce any evidence or document or any witness in rebuttal of the additional evidence produced by the appellant.