6In any case where—
(a)an election is made in the period of thirty days beginning on the day following that on which the Board give notice under paragraph 3 of Schedule 5 to the principal Act stating the expenditure in respect of which the election is made as expenditure qualifying for supplement, and
(b)after the date of that notice but on or before the date of the election, an assessment to tax or determination for the receiving field is made on or in relation to the participator making the election,
the relevant date for the purposes of paragraph 5(1) above is the date of the notice referred to in paragraph (a) above; and the assessment or determination referred to in paragraph (b) above shall be amended accordingly.