What is National Insurance?

The five NI classes (2026/27)

You stop paying NI when you reach State Pension age, regardless of whether you keep working. The threshold is £12,570 for both Class 1 and Class 4 — the same as the Income Tax Personal Allowance, by design.

How NI affects your State Pension

Your NI record determines two things:

• State Pension qualifying years — you need at least 10 years of NI contributions or credits to get any State Pension, and 35 years to get the full new State Pension (£241.30/week in 2026/27, ~£12,547.60/year).
• Specific benefit eligibility — contribution-based JSA, Maternity Allowance, Bereavement Support all check your NI record across the previous 2-3 tax years.

The should I top up state pension page works through the decision framework. The State Pension forecast calculator projects your eventual pension based on your record.

NI vs Income Tax — six key differences

The "drops to 2%" feature at £50,270 is unusual. It means high earners pay a smaller NI marginal rate than basic-rate earners (2% vs 8%) — though their income tax marginal rate is higher. The combined effect for higher earners: 42% combined marginal on the £50,270-£100,000 slice, vs 28% combined on the £12,570-£50,270 slice.

Common NI mistakes

Sources and methodology

NI rates, thresholds and class definitions from gov.uk/national-insurance-rates-letters. State Pension qualifying years from gov.uk/new-state-pension. Voluntary Class 3 rules from gov.uk/voluntary-national-insurance-contributions.

UK Tax Drag is not authorised by the Financial Conduct Authority and does not provide regulated financial advice — see the content disclaimer for the full position. The methodology page documents how every calculator is built and reviewed.

Related

• State Pension forecast calculator — project your eventual State Pension from your NI record
• Should I top up state pension? — voluntary contributions decision framework
• UK take-home tax calculator — see NI deducted alongside income tax
• Sole trader tax calculator — Class 4 NI included for self-employed
• Full UK money glossary
• FAQ library

Worked example: Class 1 NI on a £35,000 salary

The simplest way to see how employee (Class 1) National Insurance works is to run a full year through it. Take a salary of £35,000 in 2026/27, paid as a single PAYE job with no benefits-in-kind and no salary sacrifice.

That is roughly £149.53 a month of employee NI sitting alongside income tax. On the same salary, income tax is 20% of (£35,000 − £12,570) = £4,486, so NI is a little under 40% of the size of the income tax bill — a big chunk of the gap between gross and take-home pay that people often forget about. Separately, the employer pays their own NI on this worker (see below); that cost never appears on the payslip but is real money the employer commits to employing you.

Notice what does not get charged: the first £12,570 is NI-free, and because the salary is below £50,270 none of it reaches the 2% band. A worker on £60,000 would pay 8% on the slice from £12,570 to £50,270 (£3,016) plus 2% on the £9,730 above £50,270 (£194.60), totalling £3,210.60 — proving the point that the marginal NI rate falls from 8% to 2% once earnings pass the Upper Earnings Limit.

Why NI is worked out per pay period, not cumulatively

This is the single biggest practical difference between NI and income tax, and it catches people out every year. Income tax under PAYE is cumulative: HMRC spreads your Personal Allowance evenly across the year and reconciles overpayments automatically, so a bonus month is partly "smoothed out" by later months. Class 1 NI is not cumulative — it is recalculated from scratch in every single pay period against that period's thresholds.

• The £12,570 annual Primary Threshold is split into a weekly figure (£242) and a monthly figure (£1,048). NI is charged on what you earn in each period above that period's threshold.
• If you earn £8,000 in one bonus month and £2,000 the next, you pay a lot of 8% NI on the bonus month and get no automatic refund the following month — even though your annual total might be modest.
• By contrast, two people who both earn £35,000 over the year can pay different total NI if one is paid in lumpy bonuses and the other in equal monthly instalments.

There is no end-of-year NI reconciliation for most employees the way there is for income tax. This is also why salary sacrifice is so effective for NI — it reduces the gross figure in the period the contribution is made, cutting both your NI and your employer's NI at source rather than via a later claim.

Employer NI and the self-employed picture

Employer (secondary) Class 1 NI is a separate charge the employer pays on top of your wages. From April 2025 the rate is 15%, and it is charged above the Secondary Threshold — a lower starting point than the employee threshold. Most smaller employers offset part of this using the Employment Allowance. On top of that sits Class 1A (15% on most taxable benefits-in-kind such as a company car or private medical cover, reported via P11D) and Class 1B (15% on items inside a PAYE Settlement Agreement). None of these employer charges reduce your State Pension or appear on your payslip, but they are why the true cost of employing someone is well above their headline salary.

The self-employed sit on a different track:

• Class 4 is the main self-employed contribution: 6% on profits between £12,570 and £50,270, then 2% on profits above £50,270 — the same band structure as employees, just at a lower main rate. It is calculated annually through Self Assessment rather than per pay period. See the Class 4 NI guide for the full mechanic.
• Class 2 was effectively abolished as a mandatory charge from April 2024. The self-employed with profits above the Small Profits Threshold are now treated as having paid Class 2 — so they still build State Pension qualifying years without a separate bill. Those with profits below the threshold can pay Class 2 voluntarily (around £3.60/week) to protect their record, which is usually far cheaper than Class 3.
• Class 3 voluntary contributions (around £18.40/week, roughly £956.80 a year) let anyone — employed, self-employed or not working — fill a gap in their record toward the State Pension.

Because employees and the self-employed reach the State Pension through different classes but the same qualifying-year rules, it is worth confirming which contributions you are actually making. The voluntary NI decision guide and the NI gap-year analysis walk through whether topping up is worthwhile in your case.

What your NI actually buys — and how to check your record

Unlike income tax, which simply funds general spending, National Insurance is a contributory system: paying it (or being credited with it) builds personal entitlement. Your record determines:

• The new State Pension — you need 10 qualifying years to receive anything, and 35 qualifying years for the full amount (£241.30/week in 2026/27). Each missing year below 35 reduces your pension by roughly 1/35th of the full rate.
• Contributory benefits — "new style" Jobseeker's Allowance and Employment and Support Allowance, Maternity Allowance, and Bereavement Support Payment all test your NI record in recent tax years rather than your current income or savings.

Crucially, you can earn a qualifying year without paying a penny through NI credits — for example while claiming Child Benefit for a child under 12, while on certain carer's or disability benefits, or while receiving Jobseeker's Allowance. This is why the household member who claims Child Benefit matters even when income is too high to keep the payment: claiming (and then opting out of payment) still secures the credit.