(1)The rule in section 288 (the additional calculation rule) applies in relation to the calculation of receipts under—
section 277 (lease premiums),
section 279 (sums payable instead of rent),
section 280 (sums payable for surrender of lease),
section 281 (sums payable for variation or waiver of term of lease), or
section 282 (assignments for profit of lease granted at undervalue).
(2)It applies if conditions A and B are met.
(3)Condition A is that—
(a)in the case of a receipt under section 277, 279 or 280, the lease is granted out of a taxed lease,
(b)in the case of a receipt under section 281, the lease was granted out of a taxed lease, and
(c)in the case of a receipt under section 282, the assignment is of a taxed lease.
(4)A lease is a “taxed lease” for the purposes of this Chapter if—
(a)there is a receipt under any of sections 277 to 282 in respect of the lease, or
(b)there would be such a receipt, but for the operation of the additional calculation rule in the calculation of its amount.
In this Chapter such a receipt is referred to as a “taxed receipt”.
(5)Condition B is that the taxed receipt, or if there is more than one, at least one of them, has an unused amount.
(6)See section 290 for an explanation of when a taxed receipt has an “unused amount”.