Your National Insurance number is one of the most important identifiers you'll ever hold in the UK. It tracks the National Insurance you pay across your whole working life, and that record decides what State Pension and benefits you can claim later on.
Maybe you're starting your first job, you've just moved to the UK, or you simply can't put your hands on the number you know you have somewhere. This guide explains what the number is, how to get one, how to find it again, and how much National Insurance you actually pay in 2025/26.
It's written for employees, the self-employed and small business owners alike, so skip to the section that fits your situation.
What is National Insurance and how does it work?
National Insurance is a tax you pay on money you earn from employment, on profits if you're self-employed, and on wages you pay out if you're an employer.
Think of it as a contribution record that builds up your entitlement to certain state benefits over your working life.
Paying National Insurance helps you qualify for benefits including:
- the State Pension when you reach State Pension age
- contribution-based Jobseeker's Allowance
- Employment and Support Allowance
- Maternity Allowance
- Bereavement Support Payment
When do you start paying National Insurance?
You start paying National Insurance once you're 16 or over and your earnings or self-employed profits go above the relevant threshold.
The rate you pay, and the point at which you start paying, depend on:
- how much you earn
- whether you're employed or self-employed
- your age
- your residence status
Employers also pay their own National Insurance on staff wages above a separate threshold, and that's on top of what you pay yourself.
What is a National Insurance number?
Your National Insurance number is a unique reference that identifies you within the UK tax and benefits system.
It's how HMRC keeps track of every National Insurance contribution you make. Each payment is recorded against your number, so it follows you from job to job.
Why your National Insurance number matters
The number matters because it:
- records your contributions for State Pension eligibility
- links your employment history across different jobs
- connects your tax records when you're self-employed
- helps determine your entitlement to state benefits
- stays with you for life and never changes
Without one, you can't be taxed correctly through payroll, and your contributions can't be recorded properly.
Do I need a National Insurance number?
Yes. You need a National Insurance number to work in the UK, including if you work for yourself.
That applies whether you're:
- starting your first job as an employee
- beginning self-employment or freelancing
- an international student wanting to work part time
- someone who has recently moved to the UK
Can I work without one?
You can start work before your number arrives, as long as you've applied for one or can prove you have the right to work. Your employer should let you begin while your application is processed.
The catch is that your pay and contributions can't be recorded correctly until your number is in place, so apply as soon as you can.
How do I get a National Insurance number?
How you get a National Insurance number depends on your situation.
If you were born in the UK
If you were born in the UK and have a parent or guardian who claimed Child Benefit for you, you'll usually get your number automatically before your 16th birthday. You can also find it on your Personal Tax Account.
Keep any letter confirming it somewhere safe, because you'll use this number for the rest of your working life.
How to apply online
If you didn't get a number automatically, or you've moved to the UK, you can apply on GOV.UK.
The online application asks you to:
- prove your identity with valid documents
- show your right to work in the UK
- give your current UK address
- answer questions about your circumstances
National Insurance numbers for international students
International students can apply for a National Insurance number if their visa lets them work.
You'll need to show that your visa gives you the right to work, not just to study and live here. You can apply even if you don't have a job lined up yet, and applying early often makes the job search smoother.
Illustrative example: a student applying for a number
Maria is an international student from Spain. Her visa lets her work part time during term, and she wants a job in a local cafe, so she applies for a National Insurance number before she starts looking.
For her application she has:
- a valid passport
- her visa showing the right to work
- proof of her UK address (an accommodation letter)
She applies online, completes the identity steps, and receives her number by post a few weeks later. When she's hired, she gives the number to her employer so her contributions are recorded against her permanent record from day one.
This is a worked illustration, not a real client.
How long does it take?
Processing times vary, so check the current guidance on GOV.UK when you apply. Your number is posted to your UK address. If you need to start work before it arrives, tell your employer, and they can run your pay using an emergency tax code in the meantime.
How can I find my National Insurance number?
If you've lost or forgotten your number, you almost never need a new one. You just need to locate the one you already have.
Through your Personal Tax Account
The quickest way is to log in to your HMRC Personal Tax Account on GOV.UK. Your number is shown once you're signed in. You can also use the HMRC app or ask for it to be posted to you.
If you don't have an account yet, you can set one up using the GOV.UK identity verification process.
What if I've lost my number?
Don't worry. A "lost" National Insurance number just means you need to find your existing one, not replace it. The number is still valid.
Other places to find it
You can also find your number on:
- payslips from your employer
- your P60 (end-of-year tax summary)
- your P45 (when you leave a job)
- letters from HMRC about your tax
- your Self Assessment tax return
Checking the format
If you only want to check that a number is formatted correctly, the pattern is two letters, six numbers, then one letter (for example, AB 12 34 56 C). Only HMRC can confirm whether a specific number has actually been issued to a particular person.
Contacting HMRC
If you can't find your number anywhere, contact HMRC's National Insurance helpline. Have identifying details ready, such as your date of birth and address, so they can locate your record.
What does a National Insurance number look like?
A UK National Insurance number has a format that's easy to recognise.
The format
It's two letters, then six digits, then one final letter. For example: AB 12 34 56 C.
The two letters and six digits are unique to you. The final letter is A, B, C or D and has no special meaning for you personally. Some numbers are shown with spaces and some without, and both are fine.
Your number never changes
Once issued, your National Insurance number stays with you for life. It won't change if you:
- get married or enter a civil partnership
- change your name
- move abroad and come back
- change jobs
That permanence is exactly why it works as a lifelong identifier.
How do I pay National Insurance?
How you pay depends on whether you're employed or self-employed.
If you're employed
Your employer deducts any National Insurance you owe straight from your wages each pay day, and reports it to HMRC through PAYE. You'll see the deduction on your payslip. There's nothing extra for you to do.
If you're self-employed
The self-employed pay Class 4 National Insurance based on the profits reported on the Self Assessment tax return. You pay it at the same time as your Income Tax, by 31 January after the end of the tax year.
Since 6 April 2024, Class 2 National Insurance is no longer charged as a flat weekly amount. If your profits are at or above the Small Profits Threshold, you're treated as having paid it, so your contribution record is protected without an extra charge.
If you want to spread your costs, use the take-home pay calculator to see how National Insurance affects your net income, or speak to us about budgeting for your Self Assessment bill.
How much National Insurance do I pay in 2025/26?
How much you pay depends on how much you earn and how you earn it. The different types are called classes, each with its own threshold (when you start paying) and rate (how much you pay).
National Insurance rates and thresholds for 2025/26
| Who pays | What it applies to | Rate or amount |
|---|---|---|
| Employees (Class 1) | Earnings start being charged from | £12,570 a year |
| Employees (Class 1) | On earnings from £12,570 to £50,270 | 8% |
| Employees (Class 1) | On earnings above £50,270 | 2% |
| Self-employed (Class 4) | On profits from £12,570 to £50,270 | 6% |
| Self-employed (Class 4) | On profits above £50,270 | 2% |
| Employers (Class 1 secondary) | On employee earnings above £5,000 | 15% |
Understanding the rates
If you're employed, you pay 8% on earnings between £12,570 and £50,270, then 2% on anything above £50,270 for the 2025/26 tax year.
If you're self-employed, you pay Class 4 at 6% on profits between £12,570 and £50,270, then 2% above £50,270.
Rates and thresholds can change at each Budget, so always check the year you're dealing with. You can model your own figures with our National Insurance calculator.
Employer National Insurance
Employers pay on top of what employees pay. For 2025/26, employers pay 15% on employee earnings above the £5,000 Secondary Threshold. This is separate from your own contributions and doesn't reduce your take-home pay directly.
What are the different classes of National Insurance?
Knowing the classes helps you work out which applies to you.
Class 1 primary
What employees pay on wages from an employer, deducted automatically through PAYE.
Class 1 secondary
Employers' contributions, paid on top of staff wages.
Class 1A and 1B
Extra contributions employers make on certain benefits in kind, such as company cars or private medical insurance.
Class 2
For the self-employed. From 6 April 2024 it's no longer a compulsory flat weekly charge. If your profits are below the Small Profits Threshold, you can pay it voluntarily, and for 2025/26 the voluntary rate is £3.50 a week to keep your contribution record going.
Class 3
Voluntary contributions you can make to fill gaps in your record, for example where you've not worked or not earned enough in a year.
Class 4
A percentage charge on self-employed profits, paid through Self Assessment.
What if I earn under the National Insurance threshold?
Earning below the threshold usually means you don't pay anything, but it doesn't automatically mean you miss out on benefit entitlement.
National Insurance credits
If you're self-employed and your profits are between the Small Profits Threshold of £6,845 and the Lower Profits Limit of £12,570 for 2025/26, you're treated as having a qualifying contribution year for that period without paying anything. That keeps you building towards the State Pension.
If you're not working
If you're a carer, unemployed and claiming certain benefits, or unable to work through illness, you may get National Insurance credits so you don't end up with gaps in your record.
Voluntary contributions
If you can't get credits, you can choose to pay voluntary contributions to keep your record complete. Filling gaps can protect your State Pension, but it isn't always worth it, so it pays to check the numbers first.
Can I reclaim National Insurance if I overpay?
Yes. You can claim a refund if you've overpaid, which can happen if you've had two or more jobs at once or been charged in error. You apply to HMRC, and you'll need your National Insurance number and details of the overpayment.
How many years do I need for my State Pension?
Your qualifying years decide how much State Pension you get, so they're worth understanding.
The minimum
You usually need at least 10 qualifying years on your National Insurance record to get any new State Pension at all.
The full amount
To get the full new State Pension you usually need 35 qualifying years. For 2025/26 the full new State Pension is £241.30 a week, which works out at about £12,547.60 a year. If you were contracted out at some point, you may need more than 35 years.
If you have between 10 and 35 years, you generally get a proportion of the full amount. The exact figure depends on your own record, which is why it's best to check your forecast rather than rely on a rule of thumb.
What counts as a qualifying year?
A qualifying year is a tax year in which you've either:
- earned enough to pay National Insurance
- received National Insurance credits
- made voluntary contributions
Checking and filling your record
You can check your National Insurance record and State Pension forecast through your Personal Tax Account. If there are gaps, you can often pay voluntary contributions to fill them, usually going back up to six years.
Whether that's worth doing depends on how much extra pension you'd get for the cost. We can run that comparison for you so you don't pay for years you don't need.
When do I stop paying National Insurance?
You pay National Insurance on earnings above the threshold from age 16 until you reach State Pension age.
State Pension age
State Pension age is currently 66. Under current law it rises to 67 between 2026 and 2028. Once you reach it, you stop paying National Insurance even if you keep working.
Working past State Pension age
After State Pension age you don't pay National Insurance on your earnings, although you'll still pay Income Tax if any is due.
Self-employed at State Pension age
If you reach State Pension age part way through a tax year and you're self-employed, your Class 4 contributions run to the end of that tax year, then stop from the start of the next one.
No National Insurance on pensions
You never pay National Insurance on your State Pension or a private pension, whatever your age. National Insurance only applies to employment earnings and self-employed profits.
How can Zmartly help with National Insurance?
National Insurance sits inside your wider tax picture, and it gets fiddly fast once you're self-employed or running a business.
We can:
- work out exactly what you owe, whether you're employed, self-employed or both
- calculate your Class 4 contributions as part of your Self Assessment return
- advise whether voluntary contributions are worth it to protect your State Pension
- make sure your business is calculating employer National Insurance and benefits in kind correctly through our bookkeeping and payroll support
- help you claim back any overpaid National Insurance
If you're a contractor or sole trader weighing up how to draw your income, our guide for sole traders is a good starting point too.
Want to get your National Insurance right and protect your future benefits? Book a free 20-minute call with a Zmartly accountant.
Frequently asked questions
What is a National Insurance number in the UK?
A National Insurance number is a unique reference used to track your National Insurance contributions throughout your working life. It's made up of two letters, six numbers and a final letter, for example AB 12 34 56 C. It identifies you in the tax and benefits system and underpins your entitlement to the State Pension and other state benefits.
How do I apply for a National Insurance number?
You apply online on GOV.UK, where you prove your identity and your right to work in the UK. If you were born in the UK and a parent or guardian claimed Child Benefit for you, you usually get your number automatically before your 16th birthday. International students and people who've moved to the UK can apply online.
How can I find my National Insurance number?
The easiest way is to log in to your Personal Tax Account on GOV.UK or use the HMRC app, where your number is shown. You can also find it on payslips, your P60, your P45, letters from HMRC, or your Self Assessment tax return. If you still can't find it, contact HMRC's National Insurance helpline with identifying details.
What does a UK National Insurance number look like?
It follows the format two letters, six digits, then one final letter, for example AB 12 34 56 C. The final letter is A, B, C or D. Your number never changes throughout your life, even if you change your name or move abroad.
How much National Insurance do I pay in 2025/26?
For employees, you pay 8% on earnings between £12,570 and £50,270, then 2% on earnings above £50,270. The self-employed pay Class 4 at 6% on profits between £12,570 and £50,270, then 2% above that. Employers pay 15% on employee earnings above £5,000. These figures are for the 2025/26 tax year.
When do I stop paying National Insurance?
You stop paying when you reach State Pension age, currently 66 and rising to 67 between 2026 and 2028 under current law. After that you pay no National Insurance on earnings, though Income Tax may still apply. If you're self-employed and reach State Pension age mid-year, Class 4 runs to the end of that tax year.
How many years of National Insurance do I need for the State Pension?
You usually need at least 10 qualifying years to get any new State Pension, and around 35 qualifying years for the full amount. With between 10 and 35 years you generally get a proportion. Check your forecast through your Personal Tax Account for your exact position.
What's the difference between Class 2 and Class 4 National Insurance?
Class 4 is a percentage charge on self-employed profits, paid through Self Assessment (6% between £12,570 and £50,270, then 2% above for 2025/26). Class 2 used to be a compulsory flat weekly charge but, from 6 April 2024, is no longer charged where profits are at or above the Small Profits Threshold. Below that threshold you can pay it voluntarily at £3.50 a week for 2025/26 to protect your record.
