The £30,000 Retirement Mistake
Your National Insurance gap — and how to spot it before another deadline closes
A disclaimer with teeth
I'm not a financial adviser. I built a calculator. What follows is what my partner and I learned when we checked our State Pension forecasts in the run-up to early retirement, and what we plan to do about it. The numbers are right (I checked them). The decisions are yours.
Two weeks ago we started thinking seriously about retiring in 2028. Two days ago I logged in to gov.uk/check-state-pension for the first time in years. My forecast was fine — I'm essentially capped already. My partner's was missing six qualifying years, and three of them are now mathematically impossible to recover. Here's what I wish I'd understood ten years ago.
The 35-year rule, in one paragraph
The new UK State Pension pays a maximum of £241.30 per week (~£12,548/year) from State Pension Age (currently 67), but only if you've accumulated 35 qualifying years of National Insurance contributions or credits. Each year short = roughly £358/year less for life. Over a 25-year retirement that's nearly £9,000 of nominal income per missing year — and the triple-lock compounds it in real terms.
The arithmetic
Lifetime cost of missing years (assumes 21-year retirement, in today's money):
| Years missed | Annual loss | Over 21 years |
|---|---|---|
| 2 | £716/yr | £15,036 |
| 3 | £1,074/yr | £22,554 |
| 4 | £1,432/yr | £30,072 ← |
| 5 | £1,790/yr | £37,590 |
| 6 | £2,148/yr | £45,108 |
And these are nominal figures — the State Pension is triple-locked, so the real-terms cost is materially higher.
Four missing years × £358/yr × ~21-year retirement = £30,072. That's where the headline comes from. The typical case for someone who took mid-career time off for kids or worked abroad sits in the 3-to-5 missing-year range — £22k to £38k of retirement income, gone, on default settings.
How to check (free, 10 minutes)
Both you and your spouse need to do this separately. The HMRC tool is at gov.uk/check-state-pension. You'll need a Government Gateway login — set one up if you don't have one (NI number, passport or driving licence, recent payslip or P60 for ID).
The tool shows three things that matter:
- Current forecast. What you'd get if you stopped contributing today.
- Maximum forecast. What you'd get if you keep contributing until State Pension Age. If "current" matches "maximum", you're already capped — celebrate.
- Year-by-year history. Every tax year showing "Full year", "Year is not full", or "Not available". This is the gold — and the source of the bad news.
The deadline that quietly closed last April
Until 5 April 2025, HMRC ran a special extended window letting anyone fill missed qualifying years going all the way back to 6 April 2006. Beyond that date, the window snapped shut. Now you're back to the standard rule: you can only fill gaps in the most recent six tax years. So today (April 2026), you can fill back to tax year 2020-21. Anything earlier is permanent.
The point most articles bury
The 6-year window rolls forward each year. Tax year 2020-21 becomes uncloseable on 6 April 2027. So you have until then — about twelve months — to fix anything from that year. Each subsequent April you lose another year.
For my partner, three of the six missing years were pre-2020, baked into the forecast forever — undetectable until the day we logged in. That was the lesson that prompted this post.
Voluntary Class 3 contributions: the cheapest pension you'll ever buy
If you have gaps still in the fillable window, you can pay Class 3 voluntary contributions to convert them into qualifying years. The price is set by HMRC and rises slightly each year:
The Class 3 maths
Plus the triple-lock: state pension rises each year by max(CPI, earnings, 2.5%). Real-terms ROI is higher than nominal.
For comparison: I can't think of another government-backed, inflation-protected income stream you can buy at this price. A 30-year RPI-linked annuity at age 70 costs roughly £7,000–£8,000 per £358/year of income at current annuity rates. Class 3 contributions deliver the same outcome for £910.
Free NI credits: the route most people miss
Before paying voluntary contributions, check whether you can earn qualifying years for free via NI credits. There are several legitimate routes:
- Child Benefit credits. If you've claimed Child Benefit while a child was under 12 (since 1978), you've automatically been credited. Worth confirming the forecast already shows these.
- Specified Adult Childcare Credit. Look after a grandchild under 12 while their parent works? You can claim a free qualifying year per year of caring. The transferring parent's NI year goes to you. Massively underused.
- Carer's Credit. Care for someone disabled or elderly for 20+ hours a week? Free qualifying year, even if they don't claim a disability benefit.
- Universal Credit / Jobseeker's Allowance / ESA. Years on these benefits usually count automatically.
One step before paying anything: call the Future Pension Centre
This is the bit I almost skipped. Before you cheerfully transfer £910 to HMRC for any specific tax year, call the Future Pension Centre on 0800 731 0175. The advisors are free, generally helpful, and can do something the website can't:
- Confirm exactly which years are fillable for you
- Tell you which fillable years actually increase your forecast (some don't, due to transition rules between the old and new state pension)
- Quote the precise cost for each year
The reason this matters: due to the way the new state pension was bridged from the old one in 2016, paying for some specific years occasionally moves your forecast by zero. The algorithm is genuinely unintuitive. Twenty minutes on the phone before you click "pay" is twenty minutes well spent.
The spouse case is usually the urgent one
Most couples we know have one partner with a clean NI record and one with gaps from kids, part-time years, time abroad, or self-employment under the small profits threshold. The gap-bearing partner is almost always the one whose retirement plan is more sensitive to the State Pension. That's the case we ran into.
My forecast is essentially maxed. My partner's is missing six years — three lost forever to the deadline she didn't know existed, three still recoverable through some combination of Specified Adult Childcare Credit (we're heading into grandparent territory), continued employment for the next two years, and possibly a couple of Class 3 contributions in the years immediately before SPA.
If we'd done this in 2024 instead of 2026, we could have closed the lost three for about £2,700. They were undetectable behind a forecast we never bothered to look at. The annoying truth is that the system doesn't surface this — you have to go and find it.
What to do this weekend
- Both you and your spouse log in to gov.uk/check-state-pension separately. Ten minutes each.
- Screenshot both year-by-year tables.
- Identify any "Year is not full" entries within the last 6 tax years (2020-21 onwards).
- Call the Future Pension Centre on 0800 731 0175 to confirm what's fillable and what genuinely improves your forecast.
- Pay any worthwhile voluntary contributions before the next 5 April rolls another year off the cliff.
- If either of you has career breaks, future grandchild duties, or relatives needing care on the horizon, look into Specified Adult Childcare Credit and Carer's Credit.
It's a couple of hours of administrative work. For a typical couple with one gap-affected partner, the value at stake is somewhere between £20,000 and £60,000 of retirement income, depending on lifespan. Best hourly rate you'll ever earn.
And if you want to model what your numbers actually look like in retirement — with or without the State Pension at full whack — go run a scenario in the calculator. The State Pension is one of the inputs, and you can flick "include in target" on and off to see how dependent your plan is on hitting the cap.
For the regulators reading: I am still not a financial adviser. The figures used here (£241.30/week, £910 Class 3 cost, 35-year rule) are correct as of 2026-27 but rates change annually — always verify on gov.uk. Always call the Future Pension Centre before paying anything to HMRC.