The effect of a disposition of a registered estate or charge on a charge under section 237 of the Inheritance Tax Act 1984 (c. 51) (charge for unpaid tax) is to be determined, not in accordance with sections 28 to 30 above, but in accordance with sections 237(6) and 238 of that Act (under which a purchaser in good faith for money or money’s worth takes free from the charge in the absence of registration).