National Insurance · 2026/27 tax year
Class 4 National Insurance calculator UK 2026/27
Calculate the Class 4 National Insurance you owe on your self employed profits using current HMRC rates and thresholds.
Total Class 4 NI
£1,646
Class 4 NI is charged at 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270.
Understanding your results
Class 4 is often described as “NI on profits,” but practically it behaves like an extra slice of income-related contribution collected with Self Assessment. When you compare Class 4 to Income Tax on the same profit, remember both use profit after expenses — improving your expense discipline lowers both simultaneously.
The step from 6% to 2% above the upper profits limit is deliberate: higher earners still contribute, but at a lower marginal rate than on the band below. If your profit sits just under £50,270, a small increase in profit jumps a disproportionate amount through the 6% band — another marginal-rate story freelancers should internalise when pricing work late in the tax year.
Losses in one year can affect future profits for tax, but NI has its own carry-back and offset rules in limited circumstances. If you have structural losses, do not assume this headline calculator replaces loss-relief forms in your tax software.
Payments on account include Class 4 alongside Income Tax. That is why January bills feel large even when monthly “tax plus NI” mental maths looked manageable — HMRC is collecting a slice of next year early. Build the rhythm of January and July set-asides even when headlines focus on April filing.
If you incorporate, Class 4 falls away for company profits, replaced by different taxes entirely. Use this page while you remain a sole trader; revisit assumptions on any structural change to how you invoice clients.
Disclaimer: This is a guidance estimate based on the 2026/27 tax year. It is not personal tax advice — consult an accountant or HMRC for your specific circumstances.
About this calculator
Class 4 National Insurance is the main NI you pay as a self employed sole trader. It is calculated on your annual profit, not your turnover — that is, your income after deducting allowable business expenses.
For the 2026/27 tax year, you pay Class 4 NI at 6% on profits between £12,570 (the Lower Profits Limit) and £50,270 (the Upper Profits Limit). On profits above £50,270 you pay an additional 2%. There is no upper limit.
For example, if your profit is £40,000, Class 4 NI is 6% of (£40,000 - £12,570) = £1,645.80. If your profit is £80,000, you pay 6% on the first £37,700 of profit above the Lower Profits Limit (£2,262), plus 2% on the £29,730 above the Upper Profits Limit (£594.60), for a total of £2,856.60.
Class 4 NI is paid through your Self Assessment tax return, alongside your Income Tax. HMRC works out the total automatically when you submit your figures. Use this calculator to know what to expect before you file, and to set aside the right amount through the year.
Frequently asked questions
What is the difference between Class 2 and Class 4 NI?
Class 2 was a flat weekly contribution (now mostly abolished). Class 4 is a percentage of your profits and is what most sole traders pay today. They serve different purposes: Class 2 historically protected your State Pension, while Class 4 funds the wider NI system.
Do I pay Class 4 NI on my whole profit?
No — only on profit above £12,570. The first £12,570 is exempt because it is covered by the Lower Profits Limit, which is aligned with the Personal Allowance for Income Tax.
When do I pay Class 4 NI?
It is due alongside your Income Tax through Self Assessment. The deadline for the tax year ending 5 April is 31 January the following year. You may also pay through payments on account if your bill is over £1,000.
- Source: GOV.UK – Self Assessment deadlines
- Source: GOV.UK – Payments on account
Does claiming expenses reduce my Class 4 NI?
Yes. Class 4 NI is charged on profit, not turnover. So every £1 of allowable business expense reduces both your Income Tax and your Class 4 NI bill. Make sure you are claiming everything you are entitled to before filing.
How are payments on account split between Income Tax and Class 4 NI?
HMRC adds your Income Tax and Class 4 NI together and bases the two payments on account on that combined figure. Class 2 NI and Capital Gains Tax are not included in payments on account — they are settled with your January balancing payment instead.
- Source: GOV.UK – Payments on account