Dropping from five days to four on £45,000 costs £6,480.00 of take-home, which is 18.0% — not the 20% the salary cut suggests.
Reference notes for the UK tax year 2026/27, computed from HMRC's published rates rather than copied from another site.
You give up 20% of gross but less than 20% of net, because the personal allowance is a fixed amount that shelters a larger share of a smaller salary.
| Full-time salary | 4-day take-home | Cost a month | Real cut |
|---|---|---|---|
| £35,000 | £23,679.60 | £420.00 | 17.5% |
| £45,000 | £29,439.60 | £540.00 | 18.0% |
| £60,000 | £38,079.60 | £606.48 | 16.0% |
The effect is strongest at lower salaries, where the allowance is a bigger share of pay.
A reduced salary also reduces pension contributions, and holiday becomes pro rata at 22.4 days rather than 28. Some four-day-week arrangements keep full pay, in which case none of this applies.
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Full deduction breakdowns, computed on 2026/27 rates:
| Salary | Take-home a year | Take-home a month |
|---|---|---|
| £25,000 after tax | £21,519.60 | £1,793.30 |
| £35,000 after tax | £28,719.60 | £2,393.30 |
| £50,000 after tax | £39,519.60 | £3,293.30 |
| £60,000 after tax | £45,357.40 | £3,779.78 |
- Pro rata salary calculator — the general part-time calculation
- Hourly wage calculator — what an hour is worth to you
- Salary comparison calculator — compare the new package with the old
- UK tax rates and thresholds 2026/27 — every band and threshold on one page
- Take-home pay statistics — effective and marginal rates from £20,000 to £200,000, free to cite
- How the calculator works — the order of calculation and the source for every rate
- rates.json — the same figures as machine-readable JSON, no key required
- Maternity Pay Calculator UK
- Statutory Sick Pay Calculator UK
- Marriage Allowance Calculator UK
- Child Benefit Calculator UK
Full index: UK Tax & Take-Home Pay Guide — twelve guides, twelve worked salary examples and a reference table covering the whole UK system.
Figures are for the 2026/27 tax year, which runs 6 April 2026 to 5 April 2027, and were checked against gov.uk on 28 August 2026.
Rates change every April, and often at a Budget. Check the tax year a figure belongs to before relying on it.
Found a wrong number? Open an issue with the figure and a gov.uk link. Tax errors are worth fixing quickly.
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