How Claims affect Payments on Account: What are Claims
Where a claim has the affect of reducing the amount of a self-assessment in a return, it will reduce the payments on account for the following year as those payments are based on the “relevant” amount for the previous year.
The “relevant amount” being the amount by which the total income tax assessed exceeds the amount of any income tax deducted at source.
Claims made in connection with Capital Gains Tax often have a complicated effect, by deferring or increasing the tax charge, but do not affect the payments on account.
See SACM11030 for how claims affecting two or more years affect payments on account.