Can You Afford to Go Part-Time?

This article represents a personal view and is not financial advice. Tax rules and thresholds change, so please verify current figures and consider your own circumstances before making any decisions.

The question usually arrives as a feeling rather than a number: one of you wants a four-day week, or three days after parental leave, and the household reflex says we would lose a fifth of the pay, we cannot afford it. That reflex is doing the arithmetic on gross pay, and gross pay is not what you live on. Because UK tax is banded, the pounds you give up when you cut your hours are your most heavily taxed pounds, so take-home falls by less than pay does. Sometimes a lot less.

The Basic Arithmetic: Your Last Pounds Are Your Dearest

Take someone on £45,000 in England, standard tax code, no pension deduction, no student loan. Full-time, their take-home is about £2,993 a month. Drop to four days (£36,000) and gross pay falls £750 a month, but take-home falls £540, to £2,453. Drop to three days (£27,000) and take-home is £1,913. A 20% cut in pay is an 18% cut in take-home; a 40% cut in pay is a 36% cut in take-home. The gap is not dramatic at this salary because most of it sits in the basic-rate band, but it consistently runs in your favour, and it widens as pay rises.

For a higher-rate taxpayer the effect is stronger, because the pounds coming off the top were being taxed at 40% plus 2% National Insurance. On £60,000, a four-day week (£48,000) cuts gross pay by £1,000 a month and take-home by £606, from £3,780 to £3,173. That is a 20% pay cut arriving as a 16% take-home cut. In Scotland the bands and rates differ, so the exact figures do too, but the shape of the effect is the same.

A Student Loan Softens the Drop Further

Student loan repayments are 9% of everything above the plan threshold, so they shrink fast when pay falls. The same £45,000 earner with a Plan 2 loan takes home £2,876 a month full-time; at four days the drop is £473 rather than £540, because the loan repayment falls too. At three days (£27,000) this earner is below the Plan 2 threshold entirely and the repayment stops. Their take-home is then identical to a colleague with no loan at all.

The Cliffs: Where a Day Off Can Nearly Pay for Itself

The examples above are smooth curves. UK policy also has cliffs, and near a cliff the arithmetic changes character. The working-parent free childcare hours in England (30 hours a week from nine months to school age) are withdrawn completely if either parent’s adjusted net income passes £100,000, and tax-free childcare goes with them. Between £100,000 and £125,140 the personal allowance is also being tapered away, which puts the marginal rate on that slice above 60%.

Put those together for a parent on £110,000 with a child in nursery. A four-day week takes gross pay to £88,000: pay falls £1,833 a month but take-home falls £897, because the top slice was being taxed so heavily. And crossing back under £100,000 restores the free hours and tax-free childcare, which for a full-time nursery place can be worth several hundred pounds a month on its own. For that household, the fifth day of work was earning far less than it appeared to, and the day off can come close to paying for itself.

Child benefit has a gentler version of the same slope. The charge that claws it back runs from £60,000 to £80,000 of adjusted net income, 1% for every £200. A parent dropping from £70,000 to part-time hours below £60,000 keeps the full benefit, currently £27.05 a week for the eldest child and £17.90 for each other, which is about £2,300 a year for two children.

The Costs That Do Not Show on the Payslip

• Pension contributions usually scale with pay, and the employer’s contribution scales down with yours. Take-home hides this entirely: the £540 a month our £45,000 earner loses is visible, while the shrinking pension is not, and over a decade it compounds into the larger number.
• Some costs fall with the hours. A dropped day can mean a dropped nursery day and a dropped commute, and for many households the nursery day is the bigger figure of the two. Net those against the take-home drop before judging it.
• Progression is the slowest cost to surface. A part-time year is rarely just that year: it can move the timing of the next pay rise, and the forecast should say so as a dated change rather than a vague worry.

If what triggers the question is a baby rather than a standing preference, the leave year has its own arithmetic first. Maternity and paternity leave: what it really does to your finances covers the pay curve through the leave itself; this post picks up where the part-time pattern becomes the plan.

The Real Question Is Ten Years, Not Next Month

Everything above answers "what would the payslip say", and the payslip is the wrong place to stop. Affording a part-time year is not about whether next month balances; it is about whether the mortgage still clears when you planned, whether the savings floor holds through the childcare years, and where the household is in ten years under the smaller salary. That is a forecasting question, and it has a different answer for every household, which is why no article can settle it for you.

In CrestCast you model it the way it would actually happen: a dated change to the salary (say, to 0.8 of itself from next April), the nursery bill changing on the same date, and any benefit change entered as income with a date on it. Save it as a named version, keep your current plan as another, and compare the two side by side across cashflow, profit and loss and net worth. The gap between the two lines, read at year one, five and ten, is the cost of the part-time year, stated in your own numbers rather than anyone’s rule of thumb.