Subject to paragraph 7(2) below, advance corporation tax in respect of franked payments F1F2. . . required to be included in a return under this Schedule shall be due at the time by which the return for that period is to be made, and advance corporation tax so due shall be payable without the making of any assessment.

Advance corporation tax which has become so due may be assessed on the company (whether or not it has been paid when the assessment is made) if that tax, or any part of it, is not paid on or before the due date.

If it appears to F3an officer of the Board that there is a franked payment F4F5. . . which ought to have been and has not been included in a return, F6or if an officer of the Board is of the opinion that a return is incorrect, any such officer may make an assessment on the company to the best of his judgment; and any advance corporation tax due under an assessment made by virtue of this sub-paragraph shall be treated for the purposes of interest on unpaid tax as having been payable at the time when it would have been payable if a correct return had been made.