National Insurance is a fixture of UK payslips, yet most people would struggle to explain what it funds or why the amount differs between an employee, a freelancer, and a company director. It deserves better than that. Unlike income tax, which flows into general government spending, National Insurance is a contributory system tied to specific social security benefits, most importantly the State Pension. How much you pay, and whether you are paying the right class, helps determine how large your pension will be and whether you get support through sickness, unemployment, or parenthood. This guide explains the classes, the rates, and the practical checks worth making.
What National Insurance actually funds
National Insurance (NI for short) is a pay-as-you-go contribution system rather than a personal savings account, but your contribution record determines your entitlement to a set of benefits:
- State Pension — the size of your pension depends directly on your qualifying years.
- Jobseeker’s Allowance — contribution-based support while unemployed.
- Statutory sick pay — payment during periods of illness.
- Maternity, paternity, and adoption pay — statutory payments during family leave.
- Bereavement support payment — financial support following a partner’s death.
The central idea is simple: build enough qualifying years and the benefits unlock; let gaps accumulate and they shrink.
Class 1: employees and their employers
If you are employed, you pay Class 1 NI, deducted automatically through payroll. The employee rates for 2024/25 are:
| Earnings band (annual) | Employee rate |
|---|---|
| Up to £12,570 | 0% |
| £12,570 – £50,270 | 8% |
| Above £50,270 | 2% |
Your employer also pays: 13.8% on everything above the secondary threshold of £9,100. A few details are worth knowing. NI is calculated on gross income, before income tax is applied. Employer NI is paid on top of your salary rather than taken out of it, although it shapes how much employers can afford to offer in the first place. Contributions stop once you reach State Pension age. And unlike income tax, NI has no personal allowance equivalent — you start paying from the first pound above the threshold.
Class 2 and Class 4: the self-employed
People who are self-employed interact with NI twice over.
Class 2 is the cheap, flat contribution that keeps a self-employed person’s benefit record intact: £3.45 a week for 2024/25, which amounts to roughly £179 a year, payable when your annual profits exceed £12,570. If profits fall below the threshold you can still pay Class 2 voluntarily to protect your record.
Class 4 is a separate charge on profits, calculated through your Self Assessment return alongside income tax:
| Profits band (annual) | Class 4 rate |
|---|---|
| Up to £12,570 | 0% |
| £12,570 – £50,270 | 9% |
| Above £50,270 | 2% |
The distinction matters because the two classes do different jobs. Class 4 does not count towards your benefit record at all — that is what Class 2 is for.
NI credits: protecting gaps without paying
You do not have to be earning to build a record. NI credits are granted automatically in a set of circumstances: caring for someone while receiving Carer’s Allowance; claiming Jobseeker’s Allowance or Employment and Support Allowance while unemployed; receiving Statutory Sick Pay or incapacity benefits while sick or disabled; taking maternity, paternity, or adoption leave; and serving on a jury. For anyone whose career contains pauses, credits can be the difference between a complete record and a reduced State Pension.
The State Pension link
Your NI record is, in effect, your pension account. The full new State Pension for 2026/27 is £221.20 a week, and you need 35 qualifying years to receive it in full. A qualifying year is one in which you paid enough Class 1, 2, or 4 NI, received NI credits, or paid voluntary contributions. Fewer than 35 years means a proportionally reduced pension, and fewer than 10 qualifying years means you receive nothing at all.
You can check your record and projected pension at gov.uk/check-state-pension. It shows your record year by year, how many qualifying years you have, your projected State Pension, and any gaps.
Voluntary contributions: filling the gaps
Where your record has holes, voluntary contributions can plug them, and the arithmetic is often strongly in your favour. Two classes exist. Class 3 is open to anyone, at £17.75 a week for 2024/25 — about £923 a year. Class 2, at £3.45 a week, is available to self-employed people with gaps.
You can normally backfill gaps up to six years; beyond that, payment is sometimes still possible but you will need to contact HMRC. A voluntary contribution usually costs far less than the value of the additional State Pension it generates — but whether it is right for you is a personal decision that depends on your expected longevity and your other pension provision.
A worked example: £40,000 salary
Take an employee earning £40,000 a year in 2024/25. Employee Class 1 NI is 8% on the earnings between £12,570 and £40,000, so 8% of £27,430 gives £2,194 a year — roughly £183 a month. Employer NI is 13.8% on the earnings above £9,100, so 13.8% of £30,900 gives £4,264. The employer share is not deducted from the employee’s payslip, but it is part of the true cost of employing them, and it is worth understanding because it can influence salary negotiations and benefit packages. Combined, the two contributions amount to £6,458 a year.
Worth doing
National Insurance rewards small amounts of attention. Check your record on gov.uk at least once a year, because errors can go unnoticed for years. If there are gaps and you are within ten years of State Pension age, voluntary contributions are often excellent value. Keep your self-employment records straight so your Class 2 and Class 4 figures are correct. And hold on to the basics — NI and income tax are separate deductions with different thresholds, so do not file them together in the same mental spreadsheet.
For current rules and your own figures, HMRC’s National Insurance pages are the authoritative starting point, MoneyHelper’s National Insurance guide gives a plain-English overview, and GOV.UK’s State Pension forecast shows what your record is heading towards.