31Return where contingency ceases or consideration ascertained
(1)The buyer in a land transaction must make a return to the Tax Authority if—
(a)section 18(2) or 19(2) (contingent, uncertain or unascertained consideration) applies in relation to the transaction (or to any transaction in relation to which it is a linked transaction),
(b)an event mentioned in subsection (2) occurs, and
(c)the effect of the event is that—
(i)the transaction becomes notifiable,
(ii)additional tax is payable in respect of the transaction, or
(iii)tax is payable where none was payable before.
(2)The events are—
(a)in the case of contingent consideration, the contingency occurs or it becomes clear that it will not occur, or
(b)in the case of uncertain or unascertained consideration, an amount relevant to the calculation of the consideration, or any instalment of consideration, becomes ascertained.
(3)The return must be made before the end of the period of 30 days beginning with the day after the date on which the event occurred.
(4)The return must include an assessment of the tax that, on the basis of the information contained in the return, is chargeable in respect of the transaction.
(5)The tax so chargeable is to be calculated by reference to the tax rates and tax bands in force at the effective date of the transaction.
(6)This section does not apply so far as the consideration consists of rent (see schedule 19 (leases)) unless the effect of the event mentioned in subsection (2) is that the transaction becomes notifiable.