Assessment years Income Tax Act, 1961, Section 2(9), Sections 33, 80J Section 2(9) defines assessment year to be the period of 12 months commencing on the first day of April every year. It is a standard period of 12 months commencing on 1st April of every year. It does not depend upon one or the other assessee and whether or not he had a previous year relevant to a particular assessment year. It is as invariable as the calendar year. The ‘‘assessment years’’ mentioned in Sections 33 and 80-J must be read in this light. [Premier Cable Co. Ltd. v. C.I.T., (1999) 3 SCC 367 (372)]