With just weeks to go until the 5 April tax-year deadline, many savers will be scrambling to top up their pensions – but experts warn they could risk making costly last-minute mistakes.

Every March the same errors crop up, from contributions arriving too late to savers missing out on generous tax relief and allowances worth thousands of pounds.

Some misunderstand who the rules apply to, while others overlook little-known ways to boost retirement savings for family members.

The result can be missed opportunities to cut tax bills and grow pension pots before the window closes for another year.

Here, we ask pension experts about the most common pension mistakes people make each March – and how to avoid them before the deadline.

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Mistake 1: Not carrying forward unused allowances

The pension allowance is the amount you can save into your retirement pot whilst still receiving tax relief.

If you haven’t used your full pension allowance – £60,000 or 100 per cent of your annual earnings (whichever is lower) – in the previous three tax years, you may be able to carry forward unused allowance and make a much larger contribution this year.

This only applies for the last three tax years though, Chris Eastwood, chief executive of Penfold, warned.

You can use the Government calculator to work out how much allowance you have.

Mistake 2: Ignoring the £100,000 income trap

If you’re earning over £100,000 and not using your pension strategically, there’s a strong chance you’re paying more tax than you need to.

The so-called tax trap is where individuals earning between £100,000 and £125,140 lose 60 per cent of every next pound they earn to income tax.

As well as facing a 40 per cent income tax rate, people making this amount lose £1 of their £12,570 tax-free allowance for every £2 earned and the two factors combined create the high tax rate.

Eastwood said: “Between £100,000 and £125,140, the tax system quietly becomes very expensive.

“A pension contribution before 5 April can reduce adjusted net income, which can pull earnings back below the taper and recover some of what would have been lost.”

Mistake 3: Forgetting non-earning household members

Pension tax relief is not exclusively for people in employment, as some might think.

A non-working spouse, a partner on a low income, even a child, can each receive contributions of up to £2,800 per year, which HMRC rounds up to £3,600.

Eastwood said that “most families” have never been told this is an option.

He added: “The relief is there, the allowances are generous, and for most people a small amount of time spent reviewing their position before 5 April can make a real difference to their retirement savings.

“It is just a case of knowing where to look and acting before the window closes.”

Mistake 4: Triggering the MPAA without realising

Mike Ambery, retirement and savings director of Standard Life, explained that some accidentally trigger a rule that sharply limits how much they can pay into their pension each year.

Taking even a small amount of taxable income from your pension – sometimes just to “test” how withdrawals work – can activate the money purchase annual allowance (MPAA).

This means, once triggered, the amount you can contribute with tax relief drops to £10,000 per year, he said.

Ambery said: “Sometimes, people only discover this when they try to make a larger top-up at the end of the tax year and realise they’ve unintentionally restricted their own allowance.”

Mistake 5: Missing the chance to sacrifice a bonus

An annual bonus can be a welcome boost – but it can also have unintended tax consequences.

A bonus can push your income into a higher tax bracket or trigger extra changes such as the high income child benefit charge (HICBC), which applies once one parent or guardian’s income goes over £60,000 per year.

Ambery said: “What many people overlook is the option to redirect some or all of that bonus straight into their pension using salary or bonus sacrifice.

“While the rules around salary sacrifice are set to change from 2029, it remains an efficient way to contribute to your pension due to the potential to benefit from both income tax and national insurance relief.”

Salary sacrifice is when you sacrifice some of your salary, perhaps to go into a lower tax bracket, but put more into your pension.

By reducing your taxable income, it can help you avoid charges like the HICBC and boost your retirement savings at the same time.

These arrangements usually need to be set up before the bonus is paid, so it’s worth checking your options early.

Mistake 6: Not reclaiming higher-rate tax relief

Many higher and additional-rate taxpayers – 40 per cent and 45 per cent respectively – assume all their pension tax relief is applied automatically – but that depends on the type of pension you have.

Ambery said: “Many workplace pensions use ‘net pay’ arrangements, in which full tax relief is usually applied automatically through your payslip.

“However, most personal pensions and self-invested personal pensions (SIPP’s) use ‘relief at source’, and that’s where people often miss out.

“With relief at source, your provider automatically adds basic‑rate tax relief (20 per cent), but any extra relief usually has to be claimed from HMRC.”

That’s an extra 20 per cent for higher‑rate taxpayers or 25 per cent for additional‑rate taxpayers, claimed via self-assessment or by contacting HMRC directly.

Mistake 7: Forgetting pensions in divorce

Former pensions minister Ros Altmann advised those who are getting divorced to make sure they get their partner’s pension “properly valued” and “don’t just ignore it” as many people have significant value in their pensions.

Pensions are often included in divorce settlements and partners could miss out on a considerable sum if this is not considered.

Mistake 8: Paying into a loved one’s pension

If you are caring for a loved one, someone else – such as a partner – can contribute up to £2,880 per year into a pension in your name, even if you have no earnings, Altmann highlighted.

HMRC then adds tax relief, bringing the total to £3,600. The same rules apply if you have children or grandchildren.