Class 2 and Class 4 National Insurance for the Self-Employed — A Trade's Guide (2026)

What National Insurance Is and Why the Self-Employed Pay It

National Insurance Contributions (NIC) are not the same as income tax. Income tax funds general government spending; NIC is the system that builds your entitlement to certain state benefits. For the self-employed, the two that matter most are the State Pension and contributory benefits such as Maternity Allowance and certain bereavement and incapacity support.

The key concept is the qualifying year. To get the full new State Pension you currently need around 35 qualifying years on your National Insurance record (and at least 10 to get anything at all). A qualifying year is one where you've paid — or been treated as having paid — enough NIC. As a self-employed tradesperson, the contributions you make through Self Assessment are how you tick off those years. Miss too many and you reach State Pension age with a reduced payout for the rest of your life.

Class 2 NIC — The Big Reform You Need to Understand

Class 2 used to be a small flat weekly charge — a few pounds a week — that every self-employed person above a low profit threshold had to pay. It was the contribution that earned you a qualifying year for State Pension purposes. From 6 April 2024 this changed in a way that's good news for most traders but easy to misread.

Here is the rule in plain terms:

• If your profits are above the Small Profits Threshold (around £6,725 in recent years — always check the current figure on GOV.UK), you no longer have to pay Class 2 contributions. But — and this is the important bit — you are treated as having paid them. You still get the qualifying year and you still build up your State Pension and benefit entitlement. You get the credit without the cost.
• If your profits are below the Small Profits Threshold, you don't get that free credit automatically. You can, however, choose to pay Class 2 voluntarily through your Self Assessment return. The weekly rate is low — historically a little over £3.45 a week, roughly £180 for a full year — and paying it secures a qualifying year that would otherwise be missed.

That second point is the single most important planning takeaway in this guide. If you had a quiet year — long-term sick, a slow patch, a year you scaled back — and your profit dipped below the threshold, voluntarily paying Class 2 is one of the cheapest ways to protect your State Pension record. Buying back a missing year later through Class 3 voluntary contributions costs many times more. We'll come back to this with a worked example below.

Class 4 NIC — A Percentage of Your Profits

Class 4 is the contribution most self-employed traders actually pay, and it's charged as a percentage of your taxable profits — that's your income less your allowable business expenses, not your turnover. It works in bands, similar to income tax:

• Below the Lower Profits Limit (around £12,570 in recent years — the same figure as the personal allowance): you pay no Class 4 at all.
• On profits between the Lower and Upper Profits Limits (roughly £12,570 up to about £50,270): you pay the main rate. This has been set at 6% recently, having been cut from 9% in the 2024 reforms.
• On profits above the Upper Profits Limit (above about £50,270): you pay a lower additional rate of 2% on the excess.

The reason the rate drops above the upper limit is the same principle that applies to employees: NIC is weighted toward building entitlement on lower and middle earnings, so the contribution above the threshold is a flat top-up rather than the full rate.

Always verify the current figures. The thresholds and percentages above are approximate recent values and the Treasury adjusts them most years. Before you rely on any number for the tax year you're filing, check the official rates and thresholds on GOV.UK or with your accountant. The structure rarely changes; the exact figures do.

How It Appears on Your Self Assessment

You don't file or pay Class 2 and Class 4 separately. When you submit your Self Assessment return, HMRC calculates your income tax and your NIC together from the profit figure you report on your self-employment pages. The total — income tax plus Class 4, plus any voluntary Class 2 you've opted into — becomes a single bill.

That bill is due by 31 January following the end of the tax year. If your liability is large enough, you'll also be pushed into the payments on account system, where HMRC asks you to pay half of next year's estimated bill on 31 January and the other half on 31 July, on top of the balancing payment for the year just gone. Class 4 forms part of the figure used to calculate those payments on account, so a good profit year can mean a January bill that's noticeably bigger than the tax alone.

This is exactly why keeping a clean, running picture of your income and expenses through the year matters. Tools like Trade2Base let you log invoices and costs as you go, so your profit figure — and the NIC that flows from it — never comes as a nasty surprise in the new year.

Who Is Exempt or Treated Differently

Not every self-employed person pays NIC. The main exemptions and special cases are:

• Under 16: no NIC is due, whatever the profit.
• Over State Pension age: once you reach State Pension age you stop paying Class 4 (it ceases from the start of the tax year after the one in which you reach pension age) and Class 2 no longer applies. You may still owe income tax on profits.
• Profits below the Lower Profits Limit: no Class 4 is due.
• Profits below the Small Profits Threshold: no compulsory Class 2 and no automatic credit — this is the group that should consider voluntary Class 2.
• Specific occupations (such as some examiners, ministers of religion, and certain investors) have their own NIC rules — rare in the trades, but worth knowing they exist.

If you run your trade through a limited company and pay yourself a salary and dividends, you're an employee of your own company and these self-employed NIC classes don't apply in the same way — that's a different article. Everything here is aimed at sole traders.

Worked Example — A Self-Employed Electrician

Let's take Dave, a self-employed electrician. Over the tax year he invoices £62,000 and his allowable expenses — van running costs, materials, tools, insurance, accountancy, phone, a share of home-office costs — come to £17,000. His taxable profit is therefore £45,000.

His Class 4 is worked out on the slice of profit between the lower and upper limits. Using the approximate recent figures:

• Profit: £45,000
• Less the Lower Profits Limit (~£12,570): leaves £32,430 in the main band
• His profit is below the Upper Profits Limit, so none falls into the 2% band
• Class 4 at 6% on £32,430 = roughly £1,946

Because Dave's profit is comfortably above the Small Profits Threshold, he pays nothing for Class 2 but is treated as having paid it — so this year still counts as a qualifying year toward his State Pension. His Self Assessment bill will show income tax on the £45,000 (after his personal allowance) plus that ~£1,946 of Class 4, combined into one figure due on 31 January.

Now contrast that with his apprentice-turned-sole-trader mate, Liam, who had a stop-start first year and made only £5,800 of profit — below the Small Profits Threshold. Liam owes no Class 4 and no compulsory Class 2. But he also gets no automatic qualifying year. For a little over £180, Liam can tick the box on his return to pay Class 2 voluntarily, securing the year on his National Insurance record. Skipping it might feel like saving money, but it could quietly cost him a chunk of State Pension decades down the line — and buying that year back later is far more expensive.

Why Low-Profit Traders Should Often Pay Voluntary Class 2

It's worth being explicit about the logic, because it runs counter to the instinct to pay as little tax as possible:

• Voluntary Class 2 is the cheapest way to earn a qualifying year — roughly £180 versus several hundred pounds for the equivalent Class 3 top-up.
• It protects not just your State Pension but access to certain contributory benefits.
• It's a simple election made through your existing Self Assessment return — no separate process.
• The decision is most relevant in start-up years, slow years, or years with long sickness or time off, exactly when profit dips below the threshold.

Before opting in, it's worth checking your National Insurance record on GOV.UK to see whether you actually need the year — if you're already on track for 35 qualifying years, paying extra may not add anything. This is a good five-minute conversation to have with your accountant when they prepare your return.

Quick Reference: Class 2 vs Class 4

Figures shown are approximate recent values — always confirm the current thresholds and rates for your tax year on GOV.UK.

The Bottom Line for Traders

For most working sole traders the headline is simple: you no longer pay Class 2, you're still credited with it, and your real NIC cost is the Class 4 percentage on your profits — currently 6% on the middle band and 2% above the upper limit. The trap to avoid is a low-profit year where you quietly lose a qualifying year; for around £180 of voluntary Class 2 you can protect your pension record. Keep an accurate, up-to-date picture of your profit through the year with Trade2Base, set money aside for the January bill, and check the live figures on GOV.UK before you file. Get those three habits right and NIC stops being a January shock and becomes just another line you've already planned for.