A gap in your National Insurance record is a year that does not count towards your State Pension, and the government lets you buy it back. That sentence contains the whole opportunity and the whole trap. The price is published, the deadline is fixed, and whether it is worth paying depends on a question the price does not answer: would this year actually raise your pension?
What a gap is
GOV.UK lists the usual causes: employed but on low earnings, unemployed and not claiming benefits, getting credits for less than a full tax year, self-employed with profits too small to pay contributions, or living or working outside the UK (GOV.UK, Voluntary National Insurance, checked 1 November 2026).
Gaps can mean you do not have enough qualifying years to get a State Pension at all, since you usually need at least 10, or that you get less than the full rate.
The number of years that matters depends on when your record started. GOV.UK says that if your National Insurance record began after April 2016 you need 35 qualifying years for the full rate of new State Pension, and that if you were contracted out before 2016 you will usually need more than 35 (GOV.UK, The new State Pension: what you'll get, checked 1 November 2026). The full rate is £241.30 a week.
Check for free credits first
GOV.UK’s first instruction, before you pay anything, is to check whether you are eligible for National Insurance credits, because it could mean you do not have to pay at all (GOV.UK, Pay voluntary Class 3 National Insurance, checked 1 November 2026). Credits are automatic with Carer’s Allowance, Jobseeker’s Allowance and Employment and Support Allowance.
And with Child Benefit for a child under 12, and can be claimed in other situations (GOV.UK, National Insurance credits: eligibility, checked 1 November 2026).
For anyone who has spent years caring for a relative, our Carer’s Credit page is the one to read before this one. It fills the same gap, for nothing, for anyone caring 20 hours a week.
Check whether a year would help
GOV.UK’s second instruction is the one people skip: voluntary contributions do not always increase your State Pension. Check your National Insurance record and your State Pension forecast to find out whether you have gaps, whether you are eligible to pay, whether you would benefit from paying, and how much it would cost (GOV.UK, Pay voluntary Class 3 National Insurance, checked 1 November 2026).
Two situations make a paid year worthless. If your forecast already shows the full rate, or will reach it from years you will work anyway before State Pension age, an extra year adds nothing. And if a year could be filled by credits, paying for it is paying for something you could have had free. The forecast service shows the effect of each year before you commit, and GOV.UK says the Future Pension Centre can be contacted if you are below State Pension age and unsure.
What it costs
The rates for the 2026 to 2027 tax year are £18.40 a week for Class 3 and £3.65 a week for Class 2, the latter for the self-employed (GOV.UK, Voluntary National Insurance, checked 1 November 2026). A full year of Class 3 is therefore £956.80.
You usually pay the current rate. If you are paying Class 3 for the previous two tax years, or Class 2 for the previous one, you pay the rate that applied in those years; anything earlier is charged at the current rate. That means a gap gets no cheaper by waiting, and can get dearer.
The deadline
You can only pay for gaps in the past six tax years, and the deadline is 5 April each year. GOV.UK’s example: you have until 5 April 2032 to make up gaps for the 2025 to 2026 tax year (GOV.UK, Voluntary National Insurance, checked 1 November 2026). A year that falls outside the six-year window cannot be bought at any price.
If you are paying by post, the payment has to reach HMRC by 5 April, not be sent by then. For online bank payments GOV.UK says that if 5 April falls on a weekend or bank holiday, the payment must reach HMRC on the last working day before it.
Who can pay
If you are employed, you can pay Class 3 if you earn less than £129 a week and are not eligible for credits. If you are self-employed with gross income of £1,000 or less, or profits under £7,105, you can pay Class 2 or Class 3.
Different rules apply if you live or work abroad, and they changed on 6 April 2026 (GOV.UK, Check which National Insurance contributions you can pay, checked 1 November 2026). You cannot pay voluntary contributions for years that have no gap.
If you are over State Pension age, GOV.UK says to contact the Pension Service to find out whether paying would benefit you before you pay. The online forecast service is for people below pension age who are working in the UK.
How to pay
The simplest route, if you are below State Pension age and working in the UK, is the State Pension forecast service, which shows whether paying would help and lets you pay online (GOV.UK, Pay voluntary Class 3 National Insurance, checked 1 November 2026). Every other route needs the 18-digit reference number on HMRC’s payment request.
With that number you can pay by bank transfer to HMRC’s NIC Receipts account, at a bank or building society with the HMRC payslip, or by cheque by post. For gaps in the current tax year you can set up a monthly Direct Debit on form CA5603.
GOV.UK’s warning is worth repeating: using the wrong reference number can delay the payment or send it to a different tax bill. If you do not have a reference number, the forecast service can generate one, or HMRC’s National Insurance enquiries line can.
Where this fits
This page answers one question: how to buy back a missing year and whether to. What the State Pension pays, when it is paid, and how to claim it are on our State Pension guide. The payment-day table by National Insurance number, and the Christmas dates, are already on our benefit payment dates page.
Free years come first: our National Insurance credits page and grandparents’ childcare credits page cover them, and the forecast page explains why your number of years is not 35.