Four-Day Week Pay: A Complete UK Guide for 2026/27

Two Very Different Models

Before working out what a four-day week does to your pay, you need to know which of two fundamentally different arrangements is actually on offer, because they have opposite financial effects:

• Genuine four-day week ("100-80-100") — pay stays at 100% of your current salary, contracted hours reduce to roughly 80% of a standard working week, and the expectation is that output is maintained close to 100% through improved focus, fewer meetings and reduced low-value work. This is a real reduction in hours with no reduction in pay.
• Compressed hours — total weekly hours stay the same (for example 37.5 or 40 hours), simply rearranged into four longer days instead of five (roughly 9–10 hours a day instead of 7.5–8). Pay is unaffected because the total hours worked have not changed — this is a scheduling change, not a pay-for-time trade.
• Reduced-pay four-day week — sometimes offered as an alternative to redundancy or as a genuine part-time arrangement badged as "four days": pay is cut broadly in proportion to the reduced hours, similar in effect to moving to part-time work.

The phrase "four-day week" on its own tells you nothing about which of these you are being offered — always ask specifically whether pay changes, and get the arrangement confirmed in writing before assuming either outcome.

Effect on Your Effective Hourly Rate

Under a genuine 100-80-100 scheme, your annual salary is unchanged while your contracted hours fall — which means your effective hourly rate rises. Someone earning £35,000 a year on a standard 37.5-hour week has a lower implied hourly rate than the same person earning £35,000 a year on a 30-hour week; the salary and take-home pay are identical, but the value of each hour worked has increased. This is the core financial attraction of the genuine model for employees, and the core cost consideration for employers, since the same output is expected from fewer paid hours.

Compressed hours leaves your effective hourly rate unchanged, since both pay and total hours stay the same — only the daily distribution changes. A reduced-pay four-day week broadly preserves your existing hourly rate (pay falls roughly in line with hours), though the exact proportion depends on how the specific reduction is structured.

Tax and National Insurance

Income Tax and National Insurance are calculated on the salary and pay actually received in each pay period, not on the number of hours or days worked to earn it. Under a genuine 100-80-100 scheme, since your salary does not change, your Income Tax and National Insurance position does not change either — you are simply earning the same pay for less time at work. Under a reduced-pay arrangement, a lower salary generally means less Income Tax and National Insurance paid overall, and could move you into a lower tax band or below relevant thresholds if the cut is substantial — the same as any pay reduction, with nothing specific to the "four-day week" label itself.

Holiday Entitlement

Statutory minimum holiday entitlement of 5.6 weeks a year is calculated relative to your normal working pattern, not as a fixed number of days regardless of how many days you work. An employee contracted to work five days a week is normally entitled to 28 days a year (5.6 × 5); an employee contracted to work four days a week is normally entitled to 22.4 days a year (5.6 × 4). This applies whether the four-day pattern comes with a full salary (genuine model) or a reduced one — holiday entitlement follows the number of working days in your contract, not your pay level, so moving to a genuine four-day week reduces the number of holiday days even though your salary is unaffected.

Minimum Wage Compliance

National Minimum Wage and National Living Wage compliance is checked by dividing total pay for a pay reference period by the total hours actually worked in that period, not by counting days. A genuine 100-80-100 scheme automatically raises the effective hourly rate, so it never creates a minimum wage compliance problem on its own. A reduced-pay four-day week must be checked carefully for lower-paid roles: if pay is cut in exact proportion to hours, the hourly rate stays the same and compliance is unaffected — but if pay is cut by a smaller proportion than hours are reduced, or if unpaid extra tasks creep in around the edges of the shorter week, the effective hourly rate can fall below the applicable minimum wage band without anyone intending it to.

Pension Contributions

Workplace pension contributions are usually calculated as a percentage of salary or pensionable pay. Under a genuine four-day week with unchanged salary, both employee and employer pension contributions are unaffected. Under a reduced-pay arrangement, contributions fall in proportion to the lower salary, which — if the arrangement continues for years rather than being a short trial — can have a meaningful cumulative effect on retirement savings that is easy to overlook when focusing only on the immediate weekly pay change.

Your Legal Position

There is no general UK statutory right to a four-day week itself — what exists is the right to make a statutory flexible working request (available from day one of employment), which can ask for a four-day week, compressed hours, or another pattern, but which an employer can lawfully refuse for one of a specified list of business reasons. Changing your contracted hours and pay is a change to your employment contract, so it should be agreed with you, covered by an existing contractual flexibility clause, or implemented through a fair consultation process — an employer unilaterally imposing reduced hours or pay without proper process can expose itself to a breach-of-contract or constructive/unfair dismissal claim.

Official References

• GOV.UK: Flexible working
• GOV.UK: Holiday entitlement
• GOV.UK: National Minimum Wage rates