HM Revenue & Customs

Adjustments to tax 02 - Decrease in tax due because of adjustments to an earlier year

An entry will only be required in limited circumstances. These are:

or

and

To calculate the amount to decrease the tax due, you need your Tax Calculation from the earlier year. (If you don't have this, ask HMRC for a copy.) Then recalculate your liability for that year taking into account the amounts you entered into the appropriate fields in the return.

The difference between the original and recalculated figure is the amount you should enter.