Where estate duty (including estate duty leviable under the law of Northern Ireland) is chargeable in respect of any property passing on a death after 30th March 1971 and the principal value of an asset forming part of that property has been ascertained (whether in any proceedings or otherwise) for the purposes of that duty, the principal value so ascertained shall, subject to paragraph 4(3) above, be taken for the purposes of this Act to be the market value of that asset at the date of the death.

Where the principal value has been reduced under section 35 of the Finance Act 1968M1 or section 1 of the Finance Act (Northern Ireland) 1968M2 (tapering relief for gifts inter vivos etc.), the reference in sub-paragraph (1) above to the principal value as ascertained for the purposes of estate duty is a reference to that value as so ascertained before the reduction.