(1) A person who is an instalment payer for a year of assessment under section 121 shall file with the Commissioner-General by the date for payment of the first tax instalment an estimate of tax payable for the year.

(2) An estimate under subsection (1) shall, subject to any instructions by the Commissioner-General to the contrary,

(a) be in the form prescribed indicating an estimate of

(i) the assessable income of the person for the year of assessment from each employment, business and investment and the source of that income; and

(ii) the chargeable income of the person for the year and the tax to become payable with respect to that income under section 1(1)(a); and

(b) attach any other information that the Commissioner-General may require.

(3) Subject to subsection (6) and section 123(3), the tax referred to in subsection (2)(a)(ii) is the estimated tax payable by the person for the year of assessment.

(4) In estimating tax payable for a year of assessment under subsection (2)(a)(ii), a person may take into account

(a) a foreign tax credit to be claimed under section 112; and

(b) foreign income tax, only if the person has paid the tax or the person reasonably estimates that the tax will be paid during the year.

(5) The estimate of an instalment payer under subsection (1) remains in force for the whole of the basis period unless the person files a revised estimate with the Commissioner-General together with a statement of reasons for the revision.

(6) A revised estimate filed by a person under subsection (5) is the estimated tax payable by that person for the year of assessment, but only for the purposes of calculating instalments payable under section 121 after the date the revised estimate is filed with the Commissioner-General.