Career breaks are one of the biggest contributors to the gender pension gap, but there is a little-known loophole that could help mothers to mitigate some of the damage.

When a woman is on maternity leave, her employer is legally obliged to continue to pay pension contributions based on her pre-maternity salary. If the company offers pensions through salary sacrifice schemes, it has to pay both the employer and employee contributions — even if her salary drops to statutory pay. Salary sacrifice allows workers to give up part of their gross pay to put into their pension, saving them income tax and national insurance.

It means pregnant women who increase their contributions before going on leave (if they can afford to) would continue to benefit from those increased payments while they are not at work.

Say you paid £200 a month into your pot via salary sacrifice and your employer matched this, then during maternity leave the company would be responsible for paying the entire £400 contribution.

Susan Hope, a retirement and savings expert from the pension firm Scottish Widows, said: “You could have an instance where a savvy employee bumps up their salary exchange to the maximum they can, because their employer is responsible for maintaining contributions throughout the period of paid maternity leave.”

The employer would not, however, be responsible for contributions during any period of unpaid maternity leave.

Times Money last week found that some firms were wrongly reducing the amount they paid into mothers’ pensions, leading some women to miss out on thousands of pounds in their pension pots.

How to use the loophole

Employers will have differing policies on how often you can adjust your salary sacrifice arrangements. Some offer a monthly window in which you can make changes while others allow adjustments less often. Hope said that before auto-enrolment was introduced in 2012, you had to wait a year before making any alterations.

Find out how it works at your company and adjust your pension contributions as soon as you can before taking maternity leave. This will mean reducing your take-home pay, but if you can afford to, it will increase the pension pay you earn while on leave, which will not cost you anything extra.

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If your employer does not offer a salary sacrifice scheme and your pension contributions come out of your net salary after tax then the percentage that you pay in will determine the amount you pay during maternity leave. For example if you pay in the statutory 5 per cent of salary under auto-enrolment, then you will contribute 5 per cent of your maternity pay pension during your leave. Your employer’s pension contributions have to be based on your pre-maternity leave salary, in pounds and pence terms.

An employer could theoretically move pension contributions from salary sacrifice to a net pay arrangement while you were on maternity leave, which could save them money, but Hope said this was not common.

The detail will be in the small print of your employer’s pension policies, so check your paperwork before you go on leave.

There is also a risk that employers could move away from salary sacrifice schemes as a result of changes made in last year’s budget by Rachel Reeves, the chancellor. From April 2029 employees will lose some of the salary sacrifice perk that saves them money on national insurance. Any pension contributions made through salary sacrifice above £2,000 a year will become subject to national insurance. Employers will also have to pay national insurance on workers’ contributions above that level.

What difference can it make?

Women can take up to 52 weeks’ maternity leave. You get statutory maternity pay for the first 39 weeks — the first six weeks at 90 per cent of your weekly earnings, and the following 33 weeks at £187.18 a week, or 90 per cent of your weekly earnings if this is lower. Some employers pay more generous, enhanced rates of maternity pay.

The final 13 weeks, if you choose to take them, are not covered by statutory maternity pay, and it is during this time that your pension contributions are likely to stop altogether, although some employers may continue paying into your pot during this time.

This makes increasing your contributions while you can even more valuable. The wealth manager AJ Bell said that a woman earning £45,000 and paying 5 per cent of her salary into her pension pot through salary sacrifice would miss out on £563 in pension contributions during 13 weeks of unpaid leave.

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But by increasing her pension contribution to 7 per cent before her maternity leave, she would gain £675 in contributions during leave. The extra pension payment would cost her £54 a month from her pay cheque, compared with a 5 per cent contribution, but she would get £75 a month paid into her pension.

Rachel Vahey from AJ Bell said it was worth checking how quickly you would be able to lower your contributions after returning to work. “It may be that you have to continue that position, and a lower salary, for a while at least. But you will also be getting a higher pension contribution and saving on national insurance.”

Lily Megson-Harvey from the financial advice firm My Pension Expert said: “Salary sacrifice can make a meaningful difference for mums‑to‑be if it is used carefully and with foresight.”