A payment on account is a payment that is made in advance of a tax liability. In the United Kingdom, individuals who are self-employed or who have income that is not taxed at source (such as rental income or dividends) are required to make payments on account towards their tax liability for the tax year.

Payments on account are typically made in two instalments, one by the 31st of January and one by the 31st of July. The payments are based on the individual's tax liability for the previous tax year, and they are intended to help ensure that the individual pays their tax in a timely manner.

If an individual's tax liability for the current tax year is lower than their payments on account, they may be entitled to a tax refund. If their tax liability is higher than their payments on account, they may be required to pay the balance by the 31st of January following the end of the tax year.

If you are required to make payments on account towards your tax liability, it is important to ensure that you make the payments on time to avoid incurring interest and penalties. If you have any questions about payments on account or need help with your tax return, you can contact HM Revenue and Customs (HMRC) for assistance.