26(1)If, or to the extent that, a claim under paragraph 24 falls within any of Cases A to D, the Commissioners are not liable to give effect to the claim.U.K.
(2)Case A is where, in relation to the group, there is unpaid DST liability for the accounting period.
(3)Case B is where the responsible member is or will be able to seek relief by taking other steps under this Part of this Act.
(4)Case C is where the responsible member—
(a)could have sought relief by taking such steps within a period that has now expired, and
(b)knew, or ought reasonably to have known, before the end of that period that such relief was available.
(5)Case D is where—
(a)the amount paid is excessive by reason of a mistake in calculating the amount of tax payable by the group for the accounting period, and
(b)the amount was calculated in accordance with the practice generally prevailing at the time.
(6)In this paragraph “DST liability” has the same meaning as in section 66.