Appeal admission requirement: payment of tax due or advance-tax equivalent at filing; waiver allowed for sufficient reasons. Sub-section (4) of Section 249 requires payment of the tax due on returned income or, if no return filed, an amount equal to the advance tax payable before an appeal to the Appellate Assistant Commissioner is admitted; the AAC may waive this requirement for good and sufficient reasons to be recorded in writing. The ITO's report (ITNS-51) must indicate whether the requisite amount has been paid, and ITOs should add a column to report this status.