(1) In this section, "the relevant period" means, in relation to any amount -
(a) where the amount arose under section 98, the period treated in computing that amount as being the duration of the lease;
(b) where the amount arose under section 99, the period treated in computing that amount as being the duration of the lease remaining at the date of the assignment;
(c) where the amount arose under section 100, the period beginning with the sale and ending on the date fixed under the terms of the sale as the date of the reconveyance or grant, or, if that date is not so fixed, ending with the earliest date at which the reconveyance or grant could take place in accordance with the terms of the sale.
(2) Where in relation to any premises an amount has become or would have become chargeable to tax as mentioned in section 102(2) by reference to a lease, estate or interest, the person for the time being entitled to that lease, estate or interest shall, subject to this section, be treated for
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