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An individual can amend a tax return by notifying HMRC at any time after sending in the return up to 12 months following the statutory filing date. The statutory filing date is the later of the 31 January filing date for electronic returns and three months from the date the return was issued.
Where an error is discovered after the time limit for an amendment has passed, a claim for overpayment relief may be made for an individual where the error has resulted in an overpayment of tax. A claim for overpayment relief may be made no later than four years after the end of the tax year concerned.