UK NI Class 2, 3, 4 Quick Reference 2026/27 - Voluntary & Self-Employed

UK National Insurance has four employee/self-employed classes, plus a fifth class for employer contributions (Class 1A on benefits in kind). This quick reference covers the three classes most relevant to taxpayers managing their own NI position: Class 2 (voluntary self-employed), Class 3 (voluntary general), and Class 4 (compulsory self-employed).

At a glance

Class	Who pays	Rate (2026/27)	Threshold	Purpose
Class 1	Employees (auto via PAYE)	8% / 2%	£12,570 / £50,270	Compulsory; State Pension qualifying year
Class 1A	Employer (on BIKs)	15%	n/a (employer-paid)	Tax on benefits in kind
Class 2	Self-employed (voluntary)	£3.45/week	(paid voluntarily)	State Pension qualifying year for low-profit traders
Class 3	Voluntary (anyone with gap years)	£17.45/week	(paid voluntarily)	Fill State Pension qualifying-year gaps
Class 4	Self-employed (compulsory)	8% / 2%	£12,570 / £50,270	Compulsory NI on self-employment profit

Class 2 - voluntary self-employed contributions

What it is

Until April 2024, Class 2 was a flat-rate weekly contribution (£3.45/week in 2026/27) compulsory for self-employed people earning above the Small Profits Threshold (£6,725 in 2026/27).

From April 2024 onwards, Class 2 became:

• Automatic credit for self-employed people with profits above the Small Profits Threshold (no payment needed; you still get the qualifying year).
• Voluntary for self-employed people with profits below £6,725.

When to pay

Pay voluntary Class 2 if all of these apply:

• You're self-employed (registered as a sole trader with HMRC).
• Your annual profit is below £6,725.
• You don't have other income that already credits you a qualifying year (no PAYE work above the LEL, no eligible benefit credit).
• You haven't yet hit 35 qualifying years for the full new State Pension.

The cost is £179.40/year (£3.45 × 52 weeks). Each qualifying year adds approximately £6.32/week to your full State Pension - roughly £328/year of pension income for life.

How to pay

Tick the voluntary Class 2 box in your Self Assessment return (Self-Employment supplement). Pay as part of your overall SA tax bill.

If you're not already filing Self Assessment, register as self-employed first via gov.uk.

Class 3 - voluntary general contributions

What it is

Class 3 is a flat-rate voluntary contribution (£17.45/week, £907.40/year) you can pay to fill any gap year in your State Pension qualifying record.

When to pay

Pay Class 3 if any of these apply:

• You have gap years where you weren't working at all (long-term unemployment, full-time caring, study without childcare credit).
• You worked overseas in years when you weren't UK resident.
• You worked in the UK but earned below the Lower Earnings Limit (£6,396) in a year.
• You didn't claim Child Benefit during years you cared for a child under 12 (which would have credited you automatically).

How much it's worth

Each filled year adds approximately £6.32/week to your full State Pension. Cost: £907 per year filled. Break-even: approximately 3 years of retirement.

For someone with 6 missing years and 20+ years of expected retirement, the maths is overwhelmingly favourable. See our State Pension top-ups guide for the full calculation.

Key time limit

You can usually fill years going back 6 tax years. The temporary extended window (back to 2006/07) closed on 5 April 2025. From April 2025 onwards, the standard 6-year window applies.

How to pay

1. Check your State Pension forecast on your HMRC Personal Tax Account.
2. Identify the gap years and the cost shown for each.
3. Use the pay voluntary Class 3 NI service.
4. Pay by online banking with the 18-character reference, debit card, or postal cheque.
5. Verify the year shows as "full" in your record after 4-6 weeks.

Class 4 - compulsory self-employed

What it is

Class 4 is the main NI for self-employed people earning above the Lower Profits Limit. Calculated as a percentage of self-employment profit:

• 8% on profit between £12,570 (Lower Profits Limit) and £50,270 (Upper Profits Limit).
• 2% on profit above £50,270.

When you pay

Class 4 is automatic - you don't choose. If your self-employment profit exceeds £12,570, you owe Class 4 NI, calculated and paid as part of your Self Assessment return.

Worked example - £40,000 profit

Total profit:                      £40,000
Less Lower Profits Limit:         -£12,570
Profit subject to Class 4:         £27,430
× 8%:                               £2,194.40

Class 4 NI for the year:            £2,194.40

Worked example - £80,000 profit

Total profit:                      £80,000

Class 4 at 8% on £12,570 - £50,270:  £37,700 × 8% = £3,016.00
Class 4 at 2% on £50,270 - £80,000:  £29,730 × 2% =   £594.60

Total Class 4 NI:                                  £3,610.60

How to pay

Calculated automatically on your Self Assessment return. Paid as part of your overall SA tax bill on:

• 31 January following the tax year end (balancing payment + first payment on account for next year).
• 31 July (second payment on account, if applicable).

If your previous year's tax + NI exceeded £1,000, HMRC requires Payments on Account - interim payments toward next year's bill. See our self-employed NI guide for more.

Combined Class 1 + Class 4 cap

If you have both employment (Class 1) and self-employment (Class 4) income, there's an annual maximum on combined contributions. For 2026/27 the maximum is approximately:

Maximum Class 1 + Class 4 ≈ (UEL - PT) × 8%
                          = (£50,270 - £12,570) × 8%
                          = £3,016

If your combined Class 1 + Class 4 exceeds this, you can claim a refund of the excess from HMRC. Uncommon but worth checking if you have substantial mixed income.

What you can NOT do with NI

Common misconceptions:

• You cannot transfer NI between spouses. Each person's State Pension is calculated on their own NI record.
• You cannot pay extra Class 1 to boost State Pension. Class 1 is automatic via PAYE; you can't voluntarily top it up. Use Class 3 instead.
• You cannot offset NI against income tax. They are separate liabilities.
• You cannot reclaim NI in the way you can reclaim income tax for emergency-tax overpayments. NI is not refundable except in narrow circumstances (wrong category letter applied, double-deduction across two jobs above UEL, etc.).

When to talk to an accountant

Class 4 calculation is straightforward at low complexity. An accountant earns their fee when:

• You have multiple income sources interacting with the Class 1/Class 4 cap.
• You're a partner in a partnership (Class 4 calculated differently for partners).
• You have foreign-sourced self-employment income.
• You're in the £100k-£125k Personal Allowance taper zone where every £ of Class 4 saved equals 62% effective marginal rate kept.
• You're considering incorporating (Limited Company) where Class 4 disappears entirely in favour of Class 1A NIC structure.

Disclaimer

PayslipIQ provides automated educational guidance based on the figures you supply. It is not regulated tax or financial advice. NI rules interact with State Pension entitlement, Universal Credit, Working Tax Credit and Self Assessment in complex ways. For substantial decisions or unusual circumstances, contact HMRC on 0300 200 3500 (NI helpline) or use a CTA-qualified tax adviser.