Interest: Late payment interest: Special provisions: Special provisions for start dates: Over-repayment of tax
You must check whether, and from which date, the FA 2009 interest rules apply to the tax or duty you are dealing with. See CH140160 for full details.
Where an amount of income tax or capital gains tax has been repaid to a person who should not have received the repayment, we may assess and recover that amount of tax as if it were unpaid tax under section 30 TMA 1970 .
For an assessment under Section 30 TMA 1970, a special provision says that the late payment interest start date is 31 January following the tax year in respect of which the assessment is made.
See CH143340 for an example.