4(1)This paragraph applies if—
(a)a person is entitled to obtain an amount by way of repayment or drawback in respect of excise duty paid to the Commissioners,
(b)on or after the commencement day he makes a claim for the repayment or drawback, and
(c)the Commissioners fail to authorise it within the allowable period.
(2)The Commissioners must pay interest to the person on the amount for the applicable period.
(3)The allowable period is the period of 30 days starting with the day on which the Commissioners receive the claim.
(4)The applicable period is the period which—
(a)starts with the day after the allowable period ends, and
(b)ends with the day when the Commissioners authorise the repayment or drawback.
(5)Sub-paragraph (4) is subject to paragraph 6.