s 5 Basis periods
(1) For the purposes of this Act, the accounting period ending on any date within the year preceding a year of assessment shall constitute the basis period for that year of assessment. (2) In this section “accounting period”, in relation to a chargeable person, means— (a) a period of twelve months commencing on the date of the first sale or disposal of chargeable petroleum by or on behalf of that chargeable person, whichever event shall be the earlier, or commencing on such date within the calendar month in which such event occurs as may be selected by that chargeable person with the approval of the Director General; (b) such shorter period commencing as aforesaid and ending either on a date selected by that chargeable person with the approval of the Director General or on the date when that chargeable person ceases to be engaged in petroleum operations; (c) each subsequent period of twelve months during which that chargeable person is engaged in petroleum operations; or (d) any period of less than twelve months, being a period commencing on the day following the end of any such period of twelve months and ending on the date when that chargeable person ceases to be engaged in petroleum operations or on the date when that chargeable person ceases to derive income from its petroleum operations, whichever is the later. (3) Notwithstanding subsection (1) where— (a) by virtue of subsections (1) and (2) there has been taken as the basis period for a year of assessment of a chargeable person an accounting period ending on any day in the year preceding that year of assessment; and (b) there is a failure to make up the accounts of that chargeable person for an accounting period ending on the corresponding day in that year of assessment, the Director General may direct that the basis period for the following year of assessment or the basis periods for the two following years of assessment shall consist of a period or periods (which may be of any length) specified in the direction; and any period so specified for that following year of assessment and any period so specified for the later of those two following years of assessment shall constitute the basis period for that following year of assessment and for that later year respectively. Chapter 2 — Gross income