Payments on account are payments made in advance towards your tax bill. You will have to make 2 payments on account every year unless your last Self-Assessment tax bill was less than £1,000 or you have already paid more than 80% of all the tax you owe.
Each payment is half of your previous year’s tax bill and they are due by midnight on 31 January and 31
If you still have tax to pay after you’ve made your payments on account then you must make what’s called a ‘balancing payment’ by midnight on 31 January the following year. However, if you know your tax bill will be lower than the previous year you can ask HMRC to reduce your payments on account by sending an SA303 form to your local tax office.
If you don’t manage to tell HMRC and your bill does turn out lower than expected HMRC will send you a refund of the overpayment, however be careful as if you underpay you will be charged interest for the difference!
To see your payments on account log in to your HMRC Account.