Cutting your hours cuts your salary in proportion, and the calculator above shows the new gross and take-home figures. But a lower salary changes other things too. Some work in your favour, like smaller tax and student loan deductions. Others, like pension and borrowing, quietly cost more than they first appear. This guide works through what to check before you agree new hours.
A worked example: four days instead of five
Jess earns £48,000 full-time, pays 5% into a net-pay pension and repays a Plan 2 student loan. Moving to four days a week, 80% of full time, reduces the salary to £38,400.
Take-home pay falls from about £34,484 to £28,820, a drop of 16.4%, not 20%. Two things soften the fall. First, part of Jess's full-time salary was taxed at 40%, so the pay that disappears is taxed more heavily than the pay that stays. Second, the student loan repayment falls from about £1,675 to about £811, because it's 9% of earnings above a fixed threshold. For many people going part-time, the student loan is the deduction that falls fastest.
Your pension takes a bigger hit
Pension contributions are usually a percentage of pay, so both yours and your employer's fall in proportion to your salary. That's less visible than the drop in take-home pay, but over several years it adds up. In a defined-benefit scheme, a part-time year usually builds pension based on your actual part-time pay. In a pension pot, lower contributions mean less invested and less growth.
If you can afford to, consider keeping your own contribution at its full-time level in pounds, or increasing the percentage. Some employers will match a higher percentage. Others offer salary sacrifice, which makes the extra contribution cheaper because it also saves National Insurance and student loan.
Borrowing and benefits
Mortgage lenders base affordability on your current income. If you're planning to remortgage or move house, it can be easier to arrange the mortgage before reducing your hours, as long as you're honest with the lender about your plans. Credit cards and personal loans work the same way.
Lower earnings can bring you into support you didn't qualify for before. Child Benefit is no longer clawed back if a reduction takes the higher earner below £60,000. And if your household income falls far enough, Universal Credit may be worth checking. Tax-Free Childcare and funded childcare hours depend on each parent earning at least the equivalent of 16 hours a week at the minimum wage, so make sure a large cut in hours doesn't take you below that.
Formal and informal arrangements
You have the right to request flexible working, including part-time hours, from your first day in a job. Employers must consider the request properly and can only refuse for set business reasons. Once agreed, it's normally a permanent change to your contract unless you agree a trial period or a temporary arrangement. If you think you might want to return to full-time hours, ask for that possibility to be written into the agreement.
Compressed hours as an alternative
If the goal is more time rather than less work, compressed hours can be worth considering. Working full-time hours over four longer days keeps your full salary, pension and student loan position, while giving you a regular day off. It won't suit every role or every family, and long days can be tiring. But for some people it delivers most of what they want from going part-time without the 16% or more drop in take-home pay. Flexible working requests can ask for either arrangement.
Next steps
Enter your full-time salary and new pattern above to see the pro-rata figures. If you're also reducing hours around a new baby, the maternity and sick pay calculator models the leave itself, and the pro-rata holiday calculator shows your new holiday entitlement.