SolvedCH143340 | Interest: Late payment interest: Special provisions: Special provisions for start dates: Over-repayment of income tax or capital gains tax - example
From HM Revenue & Customs · Compliance Handbook
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.
Rupert’s 2012-13 ITSA return showed a repayment of £3,000. This was repaid on 14 December 2013. An enquiry into his 2014-15 return showed that Rupert had understated his profits for several years and that the tax overpaid for 2012-13 was actually only £500.
An assessment to recover the over-repayment of £2,500 was issued on 12 March 2016.
The late payment interest start date for 2012-13 is 31 January 2014.
Rupert must pay interest on the over-repayment for the period from 31 January 2014 to the date when he pays the tax.