Section 801 | Time limit on adjustment of assessment
From legislation.gov.uk
(1)This section applies if it is necessary to make an adjustment by way of assessment to give effect to an election or notice of withdrawal under section 799 or 800.
(2)The assessment is not out of time if it is made on or before the first anniversary of the normal self-assessment filing date for the tax year for which the election was made or notice was given (or treated as given).