Time is the ingredient you can't buy back

Most conversations about retirement focus on how much you save. In practice, the more powerful variable is usually how long your money has to work. A pension is simply a tax-efficient wrapper around investments, and investments grow by earning returns — then by earning returns on those returns. That process is unremarkable for the first few years and dramatic in the later ones. It needs one thing above all else: time.

If you're in your twenties or early thirties, you hold something a 50-year-old on a generous salary can never recover. Every year you leave unused is a year your money doesn't get the chance to compound.

What compound growth looks like in practice

Take a straightforward illustration. Suppose you pay £100 a month into a workplace pension from age 25 to 65 — 40 years, and £48,000 of your own money. If the investments grow by around 5% a year after charges, that pot could be worth roughly £150,000.

Notice what's doing the heavy lifting. Only about a third of that figure is money you actually handed over. The rest is growth, and most of it arrives in the final decade. Charts of pension growth tend to look flat for years and then curve sharply upwards — which is exactly why the early years feel unrewarding and matter most.

Now add an employer contribution. If your employer puts in a similar £100 a month, the pot roughly doubles to around £300,000, and half of the contributions came from someone else entirely.

Your employer and the taxman are already chipping in

This is the part that surprises people who have never looked closely at a payslip. Under automatic enrolment, most employees are placed into a workplace pension, with total contributions of at least 8% of qualifying earnings — at least 3% of which must come from the employer. You can opt out, but doing so means turning down money that is effectively part of your pay package.

Then there's tax relief. For a basic-rate taxpayer, £80 taken from your take-home pay becomes £100 inside your pension. Higher-rate and additional-rate taxpayers can usually claim the extra relief through self-assessment. If you're a basic-rate taxpayer and your employer adds 3%, every £80 you give up could become roughly £125 in your pot before any investment growth at all.

Very little else in personal finance offers that combination of free money and tax efficiency. It's worth knowing exactly what your scheme provides rather than assuming.

What delay really costs

Staying with the same assumptions, imagine you don't start until 35. You pay £100 a month for 30 years — £36,000 of your own money — and the pot reaches roughly £83,000. Ten years of delay leaves you with about half the pot, even though you paid in three-quarters as much.

To reach that £150,000 starting at 35, you'd need to contribute around £185 a month. The later you begin, the more each month has to carry, which is why catch-up contributions always feel harder than early ones.

Delay doesn't just cost you the money you didn't pay in. It costs you the growth that money would have generated, and that growth is the largest single component of a long-term pension.

Practical steps to take this month

• Check whether you're enrolled. Look at a recent payslip or your pension provider's online account. If you're not sure, ask your payroll or HR team in writing.
• Find out your contribution percentages. Knowing what you pay and what your employer pays is the starting point for every other decision.
• Increase by 1% at your next pay rise, before the extra money reaches your current account. You won't miss what you never see.
• Look at the default fund and the charges. Defaults are often perfectly reasonable, but check the annual charge and whether the fund matches your timescale.
• Track down old pots from previous jobs. Several small pensions from different employers are easy to lose sight of, and the charges may be higher than you'd expect.
• Don't opt out to boost your take-home pay unless you genuinely have no alternative. Reducing your contribution by a few pounds a month costs you far more in the long run than it saves now.

If you're starting later, start anyway

You can't recover lost years, but the arithmetic still works in your favour from today onwards. The State Pension provides a foundation, though it's rarely enough on its own to fund the retirement most people hope for.

If you're in your forties or fifties, aim for a higher percentage of your salary than the minimum, and consider whether your annual allowance — the cap on tax-relieved contributions, currently £60,000 for most people — gives you room to catch up after a bonus or a strong year.

One caution: pension money is locked away until you're 55, rising to 57 from April 2028. Keep a separate emergency fund of three to six months' expenses in easy-access savings, so you're never tempted to raid your retirement to cover a broken boiler.

And don't let pension saving crowd out everything else. Clearing high-interest debt, building a cash buffer and saving towards a first home all matter. But once those are in hand, there is no better use of a spare £50 a month than a pension started today.