Filling Gaps in Your National Insurance Record: Deadlines and How to Pay

You have found gaps in your National Insurance record and decided you want to fill them. The questions now are practical: which years can you actually pay for, how much will it cost, when are the deadlines, and how do you hand the money over. This guide answers all four, so you can fill your gaps correctly and on time rather than paying for years that do nothing or missing a deadline.

Filling gaps is one of the more valuable jobs on many people’s pre-retirement list, but the rules changed recently and the deadlines are real. Getting the sequence right is what makes sure your money actually lands where you want it.

Which Years You Can Fill

You can normally pay voluntary National Insurance to fill gaps for the last six tax years. The deadline for each year is 5 April, six years after the end of that tax year, so the window rolls forward every April.

In practice, that means gaps from 2020/21 onwards are currently available to fill, with the earliest of those, 2020/21, needing to be paid by 5 April 2027. Each later year gives you a little more time, and once a year passes its six-year deadline it can no longer be filled.

The Extended Deadline That Closed in April 2025

For a few years, a special concession let people fill gaps going all the way back to the 2006/07 tax year. That extended window closed on 5 April 2025.

If you did not pay for those older years before the deadline, they can no longer be filled, and the standard six-year rule now applies to everyone. This is worth knowing so you do not spend time chasing years that are permanently out of reach, and so you act on the years that remain open.

How Much Filling a Gap Costs

Most people fill gaps using Class 3 voluntary contributions, which cost £18.40 a week. A full year comes to £956.80, and part-years cost proportionally less.

Some self-employed people with low profits can fill a year using the cheaper Class 2 rate instead. Which class you can use depends on your circumstances in the year you are filling, so it is worth confirming before you pay, because using the wrong class can mean paying more than necessary.

How Much a Filled Year Adds to Your State Pension

A filled year adds another qualifying year, worth roughly 1/35 of the full new State Pension. At current rates, that is about £6.90 a week, or around £358 a year, for the rest of your life.

Weigh that against the cost of the year. A £956.80 outlay that returns around £358 a year can pay for itself in about three years of drawing your State Pension, with everything after that being additional income. The return is strong for most people, though it depends entirely on your own record, which is why checking comes first.

Check Your Forecast and Which Years Count First

Before paying anything, check your State Pension forecast on gov.uk and confirm which specific years would actually raise your State Pension. This is the step that saves people money, because not every gap increases what you receive.

Some years, particularly for people affected by past contracting out, will not lift your State Pension at all. The Castra team has seen people ready to pay for several years when only one or two would have made a difference, so a few minutes of checking is time well spent.

How to Pay Voluntary National Insurance: Step by Step

Once you know which years are worth filling, paying them is straightforward. The process runs in four steps:

• Check your State Pension forecast and National Insurance record on gov.uk to confirm the gaps and the years worth paying.
• Contact HMRC, or the Future Pension Centre if you are below State Pension age, to confirm the amount and that paying will boost your State Pension.
• Get your 18-digit reference number from HMRC, which you need in order to pay.
• Pay online, by bank transfer, or by cheque, using that reference so the payment is allocated to the right years.

Since April 2024, many people can also view and pay for gaps directly through the “Check your State Pension forecast” service online, which handles the reference and payment in one place.

Deadlines to Watch

The key deadline is the rolling six-year window, with each tax year needing to be paid by 5 April six years after it ends. Miss that and the year is gone for good.

Two timing points are worth flagging. First, the earliest year currently available, 2020/21, must be paid by 5 April 2027. Second, if you are close to State Pension age, pay in good time so the credit is applied before you claim, and confirm with HMRC that it will count.

Frequently Asked Questions About Filling National Insurance Gaps

How far back can I fill National Insurance gaps?

You can normally fill gaps for the last six tax years, with each year due by 5 April six years after it ends. Gaps from 2020/21 onwards are currently available. The special window that allowed filling gaps back to 2006 closed on 5 April 2025, so older years can no longer be filled.

How much does it cost to fill a National Insurance gap?

A full year of Class 3 voluntary contributions costs £956.80, at £18.40 a week, and part-years cost less. Some self-employed people with low profits can use the cheaper Class 2 rate. Always confirm which class applies to you before paying.

How do I actually pay voluntary National Insurance?

First check your forecast and confirm which years are worth paying, then contact HMRC or the Future Pension Centre to get an 18-digit reference number. You then pay online, by bank transfer, or by cheque using that reference. Many people can now also pay directly through the “Check your State Pension forecast” service on gov.uk.

Ready to Fill Your Gaps the Right Way?

Filling National Insurance gaps can add hundreds of pounds a year to your State Pension for life, as long as you pay for the right years before the deadlines. Getting that judgement right is worth a second opinion.

TL;DR: Filling Gaps in Your National Insurance Record: Deadlines and How to Pay

You can normally fill National Insurance gaps for the last six tax years, and doing it correctly can add valuable income to your State Pension for life.

• You can fill gaps for the last six tax years, with 2020/21 due by 5 April 2027.
• The window to fill gaps back to 2006 closed on 5 April 2025 and cannot be reopened.
• A full year of Class 3 voluntary National Insurance costs £956.80, and eligible self-employed people can pay the lower Class 2 rate.
• A filled year is worth around £358 a year for life, so it can pay for itself in about three years.
• To pay, get an 18-digit reference from HMRC, then pay online, by transfer, or by cheque; many can now pay through the gov.uk forecast service.
• Check your forecast first, because some gaps will not increase your State Pension.