If you know your tax bill is going to be lower than last year, you can ask HM Revenue and Customs (HMRC) to reduce your payments on account   Click on VALIDATE MY TAX RETURN   Click on YES to proceed   Answer YES to  the question Are you claiming to reduce your 2018-2019 payments on account? AND enter the AMOUNT      Enter the REASON     NOTE: If you underpay, you’ll be charged interest.