(1) Where -
(a) under or in consequence of any disposition, a charge for tax arises by reason of section 20 on a chargeable date (in this section called the first chargeable date),
(b) an accountable person has furnished all the information necessary to enable the Commissioners to ascertain the market value of -
(i) real property, or
(ii) shares which are not dealt in on a stock exchange,
comprised in the taxable inheritance so taken on the valuation date of that taxable inheritance,
(c) pursuant to an application in writing to the Commissioners on that behalf, the market value of such property on that valuation date is agreed on between that person and the Commissioners,
(d) under or in consequence of the same disposition, a charge for tax arises by reason of section 20 on either or both of the 2 chargeable dates in the years next following the year in which the first chargeable date occurs (in this section called the subsequent chargeable dates), and
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