(26) “income year”, in relation to any assessment year (hereafter in this clause, referred to as `the said assessment year’), means-
(a) the financial year next preceding the said assessment year, or
(c) such period as the Central Board of Revenue may, in the case of any person or class of persons or any source of income, specify by notification in the official Gazette,
and includes any period which, under any provision of this Ordinance, is deemed to be an income year, or in respect of which a return of total income is required to be furnished, or any income is liable to be determined or assessed, or any tax is payable.
(a) Where, in any case,-
(iii) both sub-clause (a) and sub-clause (c) apply, the income year as specified under clause (c) shall be deemed to be the income year of the assessee in respect of his income from all sources; and
(iv) the sources of income of an assessee include two or more sources in respect of which income years have been specified under clause (c), the income year of the said income years ending last shall be deemed to be the income year of the assessee in respect of his income from all sources except the sources to which clause (c) applies; and
(b) as used in sub-clause (c), “period” means any period of twelve months, or any period of more or less than twelve months, and includes any such period as may commence from, or end on, any date, including a date falling before the commencement, or after the end, as the case may be, of the financial year next preceding the said assessment year;