INTM330830 - Double Taxation applications and claims: time limit: Time limit for making assessments
HMRC may make an assessment on a taxpayer provided that it does so not later than 4 years after the end of the year of assessment to which it relates.
The time limit for making assessments is therefore the same as that for making claims. As with claims the legislation provides for longer periods for making assessments in certain cases. The legislation about the making of assessments is at TMA70/S34(1).
In cases where a loss of tax was brought about carelessly, TMA70/S36(1) provides that an assessment may be made “at any time not more than 6 years after end of the year of assessment to which it relates.”
In cases where a loss of tax was brought about deliberately, TMA70/S36(1A) provides that an assessment may be made “at any time not more than 20 years after end of the year of assessment to which it relates”.