26(1)Sub-paragraph (2) below applies where—
(a)under section 50(1) of this Act the Commissioners assess an amount of tax due from a registrable person for an accounting period and notify it to him, and
(b)the assessment is made on the basis that the amount (the additional amount) is due from him in addition to any amount shown in a return made in relation to the accounting period.
(2)The additional amount shall carry interest for the period which—
(a)begins with the day after that on which the person is required by provision made under section 49 of this Act to pay tax due from him for the accounting period, and
(b)ends with the day before the relevant day.
(3)For the purposes of sub-paragraph (2) above the relevant day is the earlier of—
(a)the day on which the assessment is notified to the person;
(b)the day on which the additional amount is paid.
(4)Sub-paragraph (5) below applies where under section 50(2) of this Act the Commissioners assess an amount as being tax due from a registrable person for an accounting period and notify it to him.
(5)The amount shall carry interest for the period which—
(a)begins with the day after that on which the person is required by provision made under section 49 of this Act to pay tax due from him for the accounting period, and
(b)ends with the day before the relevant day.
(6)For the purposes of sub-paragraph (5) above the relevant day is the earlier of—
(a)the day on which the assessment is notified to the person;
(b)the day on which the amount is paid.
(7)Interest under this paragraph shall be payable at the rate applicable under section 197 of this Act.
(8)Interest under this paragraph shall be paid without any deduction of income tax.
(9)Sub-paragraph (10) below applies where—
(a)an amount carries interest under this paragraph (or would do so apart from that sub-paragraph), and
(b)all or part of the amount turns out not to be due.
(10)In such a case—
(a)the amount or part (as the case may be) shall not carry interest under this paragraph and shall be treated as never having done so, and
(b)all such adjustments as are reasonable shall be made, including adjustments by way of repayment by the Commissioners where appropriate.