What is a balancing payment in Self Assessment?
A balancing payment is the difference between your total Self Assessment bill for a tax year and the payments on account you have already made towards it. You owe one if you earn more than HMRC estimated. For the 2025/26 tax year it is due by 11:59pm on 31 January 2027.
Figures checked against gov.uk on . General information, not tax advice.
How it is worked out
Payments on account are estimates, usually half of last year's tax each. When your return shows the real figure, the balancing payment settles the gap. gov.uk's example is a 2023 to 2024 bill of £3,000 less £1,800 already paid on account, which leaves a balancing payment of £1,200.
It is paid on the same date as the first payment on account for the following year, which explains why the January bill can feel double.
What changes the amount
Anything that moves your final bill moves the balancing payment: higher profit, a late invoice, a correction after you file, or an allowance you forgot to claim.
If you amend your return after filing, gov.uk says the change can affect your payments on account, so recheck what is due after any correction.