Section 35 | Time limit: income received after year for which it is assessable
From legislation.gov.uk
(1)Where income to which this section applies is received in a year of assessment subsequent to that for which it is assessable, an assessment to income tax as respects that income may be made at any time not more than 4 years after the end of the year of assessment in which it was received.
(2)This section applies to—
(a)employment income,
(b)pension income, and
(c)social security income.