Consequential claims etc. affecting tax liability of another person
63(1)If the effect of the exercise by any person of a power conferred by paragraph 62 would be to alter the liability to tax of another person, the power may not be exercised except with the consent in writing of that other person or, if he has died, of his personal representatives.
(2)Where such a power is exercised so as to increase the liability to tax of another person, neither paragraph 61 above nor section 43A of the [1970 c. 9.] Taxes Management Act 1970 (which makes corresponding provision in relation to income tax or capital gains tax) applies in relation to any amendment or assessment made because of that increased liability.
(3)In this paragraph “tax” includes income tax or capital gains tax.