Assessment notice powers expanded to implement appellate findings, with exclusions for time-barred cases and a quarterly deadline. Substitution of section 283 permits notice under section 280 to be issued at any time to make an assessment, reassessment or recomputation in consequence of, or to give effect to, findings or directions in orders of any authority, Tribunal or Court, or directions of the Approving Panel. The provision does not apply where the relevant tax year was already time-barred at the relevant trigger point, and the notice must be issued within three months from the end of the quarter in which the certified copy of the order is received by the jurisdictional Principal Commissioner or Commissioner.