National Insurance: The Tax Nobody Understands
National Insurance contributions (NICs) are one of the most confusing parts of being self-employed. You pay them alongside Income Tax, but they work differently, have different thresholds, and affect your entitlement to the State Pension and other benefits.
The rules changed significantly from April 2024, and many sole traders are still unsure what they actually owe. Here's the definitive guide for the 2026-27 tax year.
The Two Classes of Self-Employed NI
As a self-employed person, you may be liable for two types of NI:
Class 2 NICs - Now Voluntary
From 6 April 2024, self-employed people with profits above the Small Profits Threshold are no longer required to pay Class 2 NICs. You'll still get National Insurance credits towards your State Pension entitlement automatically.
However, if your profits are below the Small Profits Threshold (£6,845 for 2026-27), you can choose to pay Class 2 voluntarily at £3.45 per week (£179.40 per year) to build up qualifying years for your State Pension.
Why this matters: You need 35 qualifying years of National Insurance to get the full new State Pension (currently £221.20 per week). If you have gaps, voluntary Class 2 at £3.45/week is the cheapest way to fill them.
Class 4 NICs - The Main Self-Employed NI
Class 4 is the NI contribution that most self-employed people actually pay. It's calculated on your taxable profits (income minus allowable expenses) and collected via Self Assessment.
For 2026-27:
| Band | Profit Range | Rate |
|---|---|---|
| Below Lower Profits Limit | £0 - £12,570 | 0% |
| Main rate | £12,570 - £50,270 | 8% |
| Upper rate | Above £50,270 | 2% |
Key change: The main Class 4 rate was reduced from 9% to 8% from April 2024. Combined with the removal of mandatory Class 2, this was a meaningful tax cut for the self-employed.
How Much Will You Actually Pay?
Let's work through some examples for the 2026-27 tax year:
Profit: £25,000
- Class 4: (£25,000 - £12,570) × 8% = £994.40
- Class 2: Not required (profits above threshold) - £0
- Total NI: £994.40
Profit: £50,000
- Class 4: (£50,000 - £12,570) × 8% = £2,994.40
- Class 2: Not required - £0
- Total NI: £2,994.40
Profit: £80,000
- Class 4 (main): (£50,270 - £12,570) × 8% = £3,016.00
- Class 4 (upper): (£80,000 - £50,270) × 2% = £594.60
- Total NI: £3,610.60
TaxMTD calculates your NI liability automatically as part of your Self Assessment tax calculation, so you always know what you owe.
The State Pension Connection
National Insurance isn't just a tax - it builds your entitlement to:
- State Pension (35 qualifying years for the full amount)
- Maternity Allowance
- Bereavement benefits
- Employment and Support Allowance (contributory)
Even though Class 2 is no longer mandatory, you'll get National Insurance credits automatically if your profits are above the Small Profits Threshold. If your profits are below it, consider paying voluntary Class 2 to protect your pension record.
You can check your National Insurance record on GOV.UK to see how many qualifying years you have and whether you have any gaps.
NI vs Income Tax: The Combined Burden
Many sole traders focus on Income Tax and forget about NI. But the combined rates are significant:
| Profit Band | Income Tax | Class 4 NI | Combined |
|---|---|---|---|
| £12,570 - £50,270 | 20% | 8% | 28% |
| £50,270 - £125,140 | 40% | 2% | 42% |
| Over £125,140 | 45% | 2% | 47% |
And don't forget: the personal allowance is tapered for income above £100,000 (reduced by £1 for every £2 over £100,000), creating an effective 60% marginal rate between £100,000 and £125,140.
This is why maximising your allowable expenses is so important - every pound of deductible expense saves you at least 28p in combined tax and NI.
What About Employer NICs?
If you're a sole trader thinking about hiring staff, be aware that employer NICs increased to 15% from April 2025, with the threshold dropping to £5,000. This significantly increases the cost of taking on employees.
The Employment Allowance (now £10,500) helps offset this for smaller employers, but it's still a material cost to factor in.
How TaxMTD Handles National Insurance
TaxMTD calculates your NI liability as part of your overall tax position:
- Class 4 is computed automatically from your categorised income and expenses
- Payments on account include estimated NI contributions
- MTD quarterly reports give you a running estimate of your NI liability throughout the year
- The tax calculation shows Income Tax and NI separately so you can see the full picture
Key Takeaways
- Class 2 is voluntary - you don't need to pay it if your profits are above £6,845, but consider voluntary contributions if you have pension gaps
- Class 4 is 8% on profits between £12,570 and £50,270, then 2% above that
- Combined tax + NI can reach 28-47% depending on your profit level
- Track expenses carefully - every deduction saves at least 28p in the pound
- Check your NI record - gaps can cost you thousands in lost State Pension
Get started with TaxMTD and see your full tax and NI position in real time.
Further reading: Self Assessment Guide · MTD for Income Tax · UK Interest Rates: Impact on Freelancers