Class 4 National Insurance Calculator UK
Check whether you owe UK Class 4 National Insurance and estimate the annual and monthly amount from your self-employed profits. Uses the latest published GOV.UK self-employed rates for tax year 2025 to 2026.
How Class 4 National Insurance Calculator UK Works
Calculate UK Class 4 National Insurance on self-employed profits using the latest published GOV.UK 2025 to 2026 rates and thresholds. Enter your values into the form above and the calculator processes them instantly in your browser — no data is sent to any server.
What This UK Class 4 NI Calculator Checks
This page is built for one narrow job: estimating the Class 4 National Insurance bill on self-employed profits. That is a better fit for search intent than a broader self-assessment page because many people already know they are self-employed and simply want to know whether they cross the Class 4 threshold, how much the bill is likely to be, and what monthly amount to reserve. The calculator takes your annual profits and applies the latest published GOV.UK self-employed National Insurance thresholds and rates for tax year 2025 to 2026.
It also helps with the part that confuses many sole traders: the difference between Class 4 and the current Class 2 position. GOV.UK's current guidance says Class 2 contributions are treated as paid when profits are 6,845 pounds or more, and voluntary when profits are below that level. Because this page is focused on the compulsory bill most people want to estimate, the result centres on the Class 4 amount and shows the National Insurance record position as a note.
Latest Published 2025 to 2026 Rules
No Class 4 due: profits of 12,570 pounds or less
Main Class 4 rate: 6% on profits above 12,570 pounds up to 50,270 pounds
Upper Class 4 rate: 2% on profits above 50,270 pounds
Monthly reserve: annual Class 4 amount divided by 12
National Insurance record notes:
- Below 6,845 pounds: no compulsory Class 4, voluntary Class 2 may be available
- 6,845 pounds to 12,570 pounds: no Class 4, Class 2 treated as paid
- Above 12,570 pounds: Class 4 due, Class 2 treated as paid
Why a Dedicated Class 4 Page Helps
Class 4 is easy to misunderstand because it looks simple until profits cross the upper profits limit. Below that point you are paying only the main rate on the slice above the lower profits limit. Above that point, part of your profits are still charged at the main rate and only the slice over the upper profits limit drops to the lower 2% rate. A dedicated calculator removes that mental arithmetic and turns it into an immediate answer that is much easier to plan around.
This matters for cash flow. A sole trader who knows their approximate annual Class 4 bill can set aside a monthly reserve alongside income tax, VAT, and any payments on account. Even if you later use a fuller self-assessment planner, having a clean Class 4 estimate gives you one reliable component of the total bill and makes it easier to understand what part of the payment is coming from National Insurance rather than income tax.
Example Calculations
Example 1: 10,000 pounds of annual profits
- Profits are below the 12,570 pound lower profits limit
- Class 4 NI due = 0 pounds
- Because profits are above 6,845 pounds? No. Voluntary Class 2 may be available if you want to protect your record.
Example 2: 35,000 pounds of annual profits
- Profits in the main Class 4 band = 35,000 minus 12,570 = 22,430 pounds
- Main-band Class 4 NI = 22,430 times 6% = 1,345.80 pounds
- Upper-band Class 4 NI = 0 pounds
- Monthly reserve = about 112.15 pounds
Example 3: 80,000 pounds of annual profits
- Main-band profits = 50,270 minus 12,570 = 37,700 pounds
- Main-band Class 4 NI = 37,700 times 6% = 2,262.00 pounds
- Upper-band profits = 80,000 minus 50,270 = 29,730 pounds
- Upper-band Class 4 NI = 29,730 times 2% = 594.60 pounds
- Total Class 4 NI = 2,856.60 pounds
What This Page Does Not Include
This tool does not try to calculate your full self-assessment liability. It excludes income tax, student loan repayments, payments on account, pension relief, marriage allowance transfers, and any other adjustments that may affect your final return. That is deliberate. The keyword intent for Class 4 NI is usually narrower, and keeping the page focused makes it easier to use and easier to rank for a more exact search.
If you need the full planning picture, pair this page with a self-assessment planner and a payments on account calculator. That gives you a cleaner workflow: first estimate the National Insurance slice here, then look at the broader HMRC timing and savings plan on the other pages.
Frequently Asked Questions
What is Class 4 National Insurance?
Class 4 National Insurance is the profit-based National Insurance contribution paid by many self-employed people in the UK through Self Assessment. It applies only when annual profits are above the lower profits limit for the tax year. For the latest published 2025 to 2026 rates on GOV.UK, Class 4 is charged at 6% on profits over 12,570 pounds up to 50,270 pounds, and 2% on profits above 50,270 pounds.
When do I pay no Class 4 National Insurance?
You do not pay any Class 4 National Insurance if your annual self-employed profits are 12,570 pounds or less for the 2025 to 2026 tax year. If your profits are between 6,845 pounds and 12,570 pounds, Class 2 contributions are treated as paid for your National Insurance record even though you do not pay Class 4. If your profits are below 6,845 pounds, you may choose to pay voluntary Class 2 contributions to help protect your record.
Does this calculator include Class 2 National Insurance?
No. This page is focused on the Class 4 amount only. GOV.UK current self-employed National Insurance guidance says Class 2 contributions are treated as paid if profits are 6,845 pounds or more in 2025 to 2026, and voluntary if profits are below that level. Because Class 2 is no longer a compulsory bill for most self-employed people, it is shown here as a status note rather than added to the total.
When do self-employed people pay Class 4 National Insurance?
Most self-employed people pay Class 4 National Insurance through their Self Assessment tax return. The balancing payment is usually due by 31 January following the end of the tax year, and some taxpayers may also need to make payments on account.
Which tax year does this calculator use?
This calculator uses the latest published self-employed National Insurance rates on GOV.UK as checked on 27 March 2026, which are for tax year 2025 to 2026. If HMRC publishes different Class 4 rates for a later tax year, the calculation should be updated before relying on it for future-year planning.