The UK Tax Structure
In the United Kingdom, income tax is collected by HM Revenue and Customs (HMRC) using a system called PAYE (Pay As You Earn) for employees. Tax is applied to wages, pensions, and most other savings or investment interest. The UK tax year runs from the 6th of April to the 5th of April of the following calendar year.
The Personal Allowance
Most residents in the United Kingdom qualify for a tax-free Personal Allowance. For the 2025-26 tax year, the standard Personal Allowance is £12,570. You pay no income tax on any earnings up to this threshold.
Income Tax Bands
Earnings above your Personal Allowance are taxed in progressive bands:
The Personal Allowance Taper (The '60% Tax Trap')
If your adjusted net income exceeds £100,000, your Personal Allowance is reduced by £1 for every £2 of income above that limit. This taper completely eliminates the Personal Allowance once income reaches £125,140. This reduction creates an effective marginal tax rate of 60% on earnings between £100,000 and £125,140, as you pay 40% income tax and lose tax-free allowances simultaneously.
National Insurance (NI) Contributions
In addition to income tax, employees must pay National Insurance (Class 1) to fund state pensions and healthcare. The Class 1 rate for 2025-26 is:
Conclusion
Understanding your tax bands and NI contributions helps you plan salary sacrifice arrangements (such as additional workplace pension contributions) to stay below key thresholds and optimize take-home pay.