When you’re employed, National Insurance is straightforward: your employer deducts it before you see your pay. When you’re self-employed, the picture looks different. You’re responsible for two separate classes of contribution — Class 2 and Class 4 National Insurance — both of which are settled through your Self Assessment tax return each January.

Understanding what Class 2 and Class 4 National Insurance are isn’t just a box-ticking exercise. The amounts involved can be significant, particularly Class 4 once your profits grow, and Class 2 contributions have a direct bearing on whether you’re building entitlement toward your State Pension. Getting to grips with both is worth doing properly, not least because the rules have shifted in recent years and there are still some common misunderstandings about what actually needs to be paid.

Class 2 National Insurance used to be a fixed weekly charge that self-employed individuals paid separately throughout the year. That changed from April 2024, and the system has simplified considerably since.

For 2026/27, if your self-employed profits are £7,105 or more, you are treated as having paid Class 2 contributions automatically. No separate payment, no form to fill in — the entitlement is credited when you file your Self Assessment return. This threshold is referred to as the Small Profits Threshold.

If your profits fall below £7,105, you won’t be treated as having paid Class 2, which means that year may not count as a qualifying year toward your State Pension. In that situation, you can choose to pay voluntary Class 2 contributions at £3.65 per week for 2026/27 to protect your record. Whether that’s worth doing depends on how many qualifying years you already have and how far away you are from State Pension age.

To put the pension point in context: you need 10 qualifying years on your National Insurance record to receive any new State Pension at all, and 35 qualifying years to receive the full amount (assuming you had no NI record before 6 April 2016). A missing year early in your self-employment career can cost you more than the £190 or so it would have taken to plug it voluntarily.

Class 4 is the bigger of the two contributions for most self-employed people, and it works more like Income Tax — it’s calculated as a percentage of your profits above a threshold, not a flat weekly amount.

For 2026/27, the rates are:

• 6% on profits between £12,570 and £50,270
• 2% on profits above £50,270

The £12,570 figure is the Lower Profits Limit and aligns with the Income Tax Personal Allowance. The £50,270 figure is the Upper Profits Limit, which also aligns with the higher-rate Income Tax threshold. So if your profits sit between those two numbers, you’re paying 6% on everything in that band. Once you’re above £50,270, the rate drops to 2% on the excess — the same logic as the reduction in employee NI at the Upper Earnings Limit.

To illustrate: if your self-employed profits are £35,000 in 2026/27, your Class 4 liability is 6% of the difference between £35,000 and £12,570, which works out at £1,345.80. On top of that you’ll have Income Tax to consider, but the two calculations run separately.

Both Class 4 and the automatic Class 2 credit are handled through your Self Assessment return, so there’s no separate payment mechanism to worry about — it all comes out in the January payment.

One thing that gets overlooked is the relationship between self-employed NI contributions and State Pension entitlement. Class 4 contributions do not count toward your State Pension record. Only Class 2 does.

This is worth remembering if your profits are consistently above the Small Profits Threshold, because you’re building your State Pension record through the automatic Class 2 credit each year. If your profits drop below £7,105 in a given year — perhaps because you had a quiet patch or took extended time off — that year’s entitlement isn’t automatic. You’d need to pay voluntary Class 2 contributions (£3.65 per week in 2026/27) to protect that year’s record.

There’s a separate option to pay voluntary Class 3 contributions if you’ve never been self-employed, though the rules around paying voluntarily for periods spent abroad have tightened from April 2026. For most UK-resident self-employed individuals, that change doesn’t affect them directly, but it’s worth being aware of if your circumstances have involved time working outside the UK.

The main takeaway: once your profits clear the Small Profits Threshold, your State Pension record looks after itself. Below that threshold, it’s worth taking five minutes to work out whether a voluntary top-up makes sense for the year.

Not everyone who files a Self Assessment return will owe either class of NI contribution. There are a few situations where that’s the case.

If your self-employed profits are below the Small Profits Threshold (£7,105 for 2026/27), you won’t be treated as having paid Class 2 — and you won’t owe any Class 4 either, since Class 4 doesn’t kick in until profits exceed £12,570. You may still want to consider voluntary Class 2 payments for pension purposes, but it’s a choice rather than an obligation.

If you’re a company director drawing a salary and dividends through your limited company rather than operating as a sole trader or freelancer, you’re not self-employed for NI purposes. Directors pay Class 1 employee NI on their salary through PAYE — a different mechanism entirely. The Class 2 and Class 4 rules simply don’t apply to that income.

Similarly, if you’re a landlord with rental income but no other self-employed trade, rental profits don’t attract Class 2 or Class 4 NI. Property income sits in its own category for tax purposes. It’s a distinction worth knowing, particularly for clients who have a mix of employment, rental, and self-employed income all appearing on the same return.