National Insurance for the self-employed is one of those topics that looks simple on the surface and gets surprisingly confusing once you dig into it. Most sole traders know they pay something — but the mechanics of which class, at what rate, and on what basis often stay murky until the Self Assessment bill lands.

The short version: as a self-employed person in the UK, you’ll typically deal with two types of National Insurance contribution — Class 2 and Class 4. They work on different bases, serve different purposes, and are calculated separately. Understanding both matters not just for budgeting purposes, but because one of them directly affects your entitlement to a state pension.

This post walks through how each class works for the 2026 to 2027 tax year, what the thresholds mean in practice, and a few things worth knowing before your next Self Assessment return.

When you’re employed, National Insurance is handled by your employer through PAYE. Class 1 contributions are deducted from your pay automatically, with your employer also contributing on top. You don’t need to think about it — it just happens.

Self-employment removes that convenience. There’s no employer deducting NI on your behalf, so you’re responsible for calculating and paying it yourself, usually through your annual Self Assessment tax return.

For 2026 to 2027, employees pay Class 1 NI at 8% on weekly earnings between £242 and £967, and 2% on anything above that. Self-employed individuals pay neither of those rates — instead, you pay Class 2 and Class 4 contributions, which are calculated on your profits rather than your gross earnings, and at lower rates than most employees realise.

That distinction — profits, not turnover — is important. Your allowable business expenses are deducted first, and National Insurance is then worked out on what’s left. It’s one of the genuine advantages of self-employment, and it’s why keeping accurate records of your costs matters beyond just good housekeeping.

Class 4 National Insurance is the bigger of the two liabilities for most self-employed people with healthy profits. For the 2026 to 2027 tax year, the rates are:

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

The lower rate above £50,270 mirrors the tapering you see with Class 1 contributions for higher earners — the idea being that NI shouldn’t represent an ever-increasing share of income as profits grow.

To put this in practical terms: if your self-employed profits for 2026/27 are £35,000, your Class 4 liability works out at roughly £1,345 — calculated on the £22,430 of profit between the £12,570 threshold and your profit figure. That’s a meaningful number to factor into your cash flow planning, particularly if you’re new to self-employment and haven’t been setting aside tax throughout the year.

Class 4 contributions don’t count towards your National Insurance record for state pension purposes. They’re essentially a separate levy on self-employed profits. That’s where Class 2 becomes important — which leads us to the next section.

Class 2 National Insurance is charged at a flat weekly rate — £3.65 per week for 2026 to 2027. That works out at just under £190 for a full tax year, which is relatively modest. But the reason it matters disproportionately is that Class 2 contributions are what build your entitlement to the state pension and certain other contributory benefits, including the Employment and Support Allowance.

Here’s how it works in practice for 2026/27: if your self-employed profits are £7,105 or more for the year, your Class 2 contributions are treated as having been paid — even though you don’t physically hand money over. HMRC credits your National Insurance record automatically. You get a qualifying year without writing a separate cheque.

If your profits fall below £7,105, there’s nothing automatically due — but you can choose to pay voluntary Class 2 contributions at £3.65 per week if you want to protect your NI record. For someone who’s had a low-income year and has gaps they want to fill, that’s extremely cost-effective compared to the alternative.

The interaction between Class 2 and state pension entitlement is something we encourage clients not to overlook, especially in early years of self-employment when profits are modest and the temptation is to focus entirely on cash flow.

If your self-employed profits sit below the £12,570 threshold, you won’t owe any Class 4 NI. That threshold aligns with the personal allowance for Income Tax, so below that point, no Class 4 applies.

If your profits are between £7,105 and £12,570, your Class 2 contributions are still treated as paid (protecting your NI record) and you simply won’t owe Class 4. Net result: no NI bill, but a qualifying year for state pension purposes. That’s a genuinely good outcome for someone who’s had a quiet year.

If your profits fall below £7,105, nothing is automatically credited — and nothing is automatically due either. This is the point where voluntary contributions become worth considering. At £3.65 a week, paying voluntarily for a full year costs less than £190. Given that you need 35 qualifying years for a full state pension, plugging a gap year that cheaply makes strong financial sense in most cases.

One thing worth knowing: from 6 April 2026, the rules around voluntary Class 2 contributions for periods spent working abroad changed significantly. If that applies to your situation — perhaps you freelance across borders or have worked internationally — it’s worth taking specific advice, as the old rules no longer apply in the same way.

The mechanics are straightforward for most people: both Class 2 and Class 4 NI are calculated as part of your Self Assessment tax return and paid alongside your Income Tax. You don’t need to make separate payments to HMRC — it all comes through the same Self Assessment bill, due by 31 January following the end of the tax year.

If you’re on the payment on account system (which HMRC applies when your Self Assessment bill exceeds a certain threshold), you’ll also make advance payments towards the following year’s liability in January and July. This can catch people out if they’ve had a significantly better year than expected — the bill in January can include both the balancing payment for the year just ended and the first payment on account for the current year.

The practical implication: set money aside as you go. A rough rule of thumb for sole traders with modest profits is to put aside around 25-30% of income throughout the year to cover both Income Tax and NI. If your profits are higher, that percentage should rise. If you’re unsure of the right number for your situation, that’s exactly the kind of thing a decent accountant will model out for you upfront rather than leaving you to guess.

Most people pay Class 2 and Class 4 through Self Assessment without needing to do anything separately — HMRC works it out from the profit figure you report.