The pension annual allowance is the maximum amount of money that an individual can contribute to their pension each year and receive tax relief on. In the United Kingdom, the pension annual allowance is set by the government and is subject to change from year to year.

The pension annual allowance applies to all types of pension schemes, including defined benefit and defined contribution schemes. It applies to both employer and employee contributions, and it is calculated on a tax year basis (6 April to 5 April).

If an individual's contributions to their pension exceed the pension annual allowance in a given tax year, they may be subject to a tax charge. The tax charge is based on the excess contributions and is calculated at the individual's marginal tax rate.

It is important to be aware of the pension annual allowance, as it can affect an individual's ability to save for their retirement and their tax liability. If you have any questions about the pension annual allowance or need help with your pension planning, you can contact HM Revenue and Customs (HMRC) or a financial advisor for assistance.