Section 40 | Election for transfer of allowance under section 39
From legislation.gov.uk
(1)An election under section 39—
(a)must be made not more than 4 years after the end of the tax year to which it relates, and
(b)cannot be withdrawn.
(2)If an individual makes an election for a tax year under section 39 the individual is treated as also giving notice under section 51(4) that section 51(1) (tax reductions for married couples and civil partners: transfer of unused relief) is to apply for the tax year.