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 2017-2018 payments on account? AND enter the AMOUNT
Enter the REASON
NOTE: If you underpay, you’ll be charged interest.