Self-Employed National Insurance Calculator (2025/26)
Use our free self-employed National Insurance calculator to work out your Class 2 and Class 4 National Insurance on your profit for the 2025/26 tax year (6 April 2025 – 5 April 2026).
Self-employed National Insurance: Class 2 and Class 4 explained
This self-employed National Insurance calculator covers Class 2 and Class 4 for sole traders, who pay National Insurance through their Self Assessment tax return.
Since April 2024, Class 2 is £0 for most self-employed people – the old flat weekly charge was scrapped for everyone with profits above the Small Profits Threshold. Class 4 is a percentage of your profits and remains payable.
National Insurance rates and thresholds (2025/26)
| Class 2 (weekly) | Annual profit | What you pay |
|---|---|---|
| Below Small Profits Threshold | Under £6,845 | £0 due – £3.50/week voluntary |
| SPT to Lower Profits Threshold | £6,845 – £12,570 | £0 (NI credits earned) |
| Above Lower Profits Threshold | £12,570+ | £0 |
| Class 4 (annual) | Annual profit | Rate |
|---|---|---|
| Below Lower Profits Limit | Up to £12,570 | 0% |
| Main rate | £12,570 – £50,270 | 6% |
| Additional rate | Over £50,270 | 2% |
Why the Class 2 reform matters
If your profit is between £6,845 and £12,570 you automatically build up a National Insurance record without paying anything – that record counts towards your State Pension.
If your profit is below £6,845 you get no record automatically. You can, however, pay Class 2 voluntarily at £3.50 a week (about £182 a year) to keep your record complete.
For many people that is the cheapest way to protect a year of State Pension entitlement – far less than a voluntary Class 3 contribution.
How to pay
Class 2 and Class 4 are paid together with Income Tax through Self Assessment, normally by 31 January following the end of the tax year. Register for Self Assessment on gov.uk if you have not already.
Self-employed National Insurance calculator FAQs
Do I pay NI if my profit is below £6,845?
No Class 2 or Class 4 is due below the Small Profits Threshold, but you can pay Class 2 voluntarily at £3.50 a week to protect your NI record and State Pension.
Is paying voluntary Class 2 worth it?
Usually yes if you want a complete NI year for State Pension purposes – £3.50 a week is far cheaper than a Class 3 voluntary contribution (£17.75 a week in 2025/26).
What is the difference between Class 2 and Class 4?
Class 2 is a flat weekly rate tied to the Small Profits Threshold (now £0 for most); Class 4 is a percentage of profit between £12,570 and £50,270 (6%) and above £50,270 (2%).
When do I pay it?
With your Self Assessment bill, normally by 31 January after the tax year ends.
How is Class 4 calculated above £50,270?
6% on £12,570–£50,270 (£2,262) plus 2% on everything above £50,270.
Do I pay Class 4 after State Pension age?
No – if you are over State Pension age at the start of the tax year, you do not pay Class 4.