27(1)If after a Revenue determination has been made the purchaser delivers a land transaction return in respect of the transaction, the self-assessment included in that return supersedes the determination.
(2)Sub-paragraph (1) does not apply to a return delivered—
(a)more than six years after the day on which the power to make the determination first became exercisable, or
(b)more than twelve months after the date of the determination,
whichever is the later.
(3)Where—
(a)proceedings have been begun for the recovery of any tax charged by a Revenue determination, and
(b)before the proceedings are concluded the determination is superseded by a self-assessment,
the proceedings may be continued as if they were proceedings for the recovery of so much of the tax charged by the self-assessment as is due and payable and has not been paid.