(1) Subject to this section, income shall accrue to a person for the purposes of this Act—
(a) in the case of income from employment, when it is earned;
(b) in the case of a business, in relation to which the Comptroller is satisfied that a commercially recognised system of accounting other than a cash received basis is regularly followed, when it is credited in the books of account of such person;
(c) in the case of a business, where, under subsection (2), the Comptroller has accepted the preparation by that person of his or her accounts on a cash received basis, when it is received by him or her; or
(d) in any other case, when it becomes due and payable to him or her.
(2) Where any person regularly prepares the accounts of his or her business on a cash received basis the Comptroller may, on application and in his or her discretion, accept such method of accounting or may direct that accounts be prepared on an accrual basis and the income accrued to such person shall be ascertained accordingly.
(3) Subsection (2) shall not be construed to prevent the Comptroller from directing the adoption of an accrual basis in respect of a particular person or class of persons for any year of income by reason only that a cash received basis had been accepted in respect of previous years.
(4) Where an amount that would otherwise have accrued to a person when it was received by him or her is not paid to him or her but is reinvested, accumulated, carried to any reserve or otherwise dealt with on his or her behalf or as he or she directs, it shall be deemed to have accrued to him or her on the date it is so dealt with.
(5) Income shall not cease to have accrued to any person within the meaning of this section by reason only of the cessation of a source of income prior to the receipt of any amount from such source.