Four-day week

Two models behind one label

“Four-day week” describes the calendar, not the hours. Before anything else, decide which of these you mean:

GOV.UK lists compressed hours as a type of flexible working: full-time hours over fewer days. The UK pilot below tested the reduced-hours version with full pay. Say which one you mean in the job ad, with the weekly hours written out. “Four-day week” alone leaves a candidate guessing whether the fifth day costs them longer shifts.

What the UK pilot measured

The UK pilot ran from June to December 2022 and was reported in February 2023 by Autonomy with researchers at the University of Cambridge and Boston College, who describe it as the largest four-day week trial to that date. It covered 61 companies and around 2,900 workers. Pay stayed at 100% and each company had to give staff a “meaningful” reduction in working time, in whatever shape suited it: a classic Friday off, staggered or decentralised days, annualised hours or a conditional entitlement.

At the end, 56 of the 61 companies were continuing with the four-day week and 18 had made it permanent. Among the 23 companies that supplied revenue data, revenue stayed broadly the same over the trial, rising 1.4% on average when weighted by company size. Between the comparison period and the trial, resignations fell from 2 to 0.8 per 100 employees, and sick and personal days from 2.0 to 0.7 per employee per month.

Read those numbers with care. The companies volunteered and had two months of preparation support, and the authors say that, partly because the sample was small, they cannot call the resignation, hiring and absence trends statistically significant. The pilot shows that a reduced-hours week can work for employers who want it and prepare for it; it does not predict what happens in a business that has not.

Legal points in Great Britain and the US

Great Britain. Since 6 April 2024, employees in England, Scotland and Wales can make a statutory flexible working request from their first day in a job, under the Flexible Working (Amendment) Regulations 2023. They can make two requests in any 12 months. You must decide within two months unless the employee agrees to longer, discuss the request with them before refusing, and refuse only for one of the business reasons GOV.UK lists. That is the rule on 3 October 2026. Under the Employment Rights Act 2025, Acas expects a change in 2027 that will also require you to explain why a refusal is reasonable. Northern Ireland has different flexible-working rules. Either model usually changes the contract: the written statement of employment particulars records hours and days of work as well as pay, so moving people onto longer days, or cutting their hours or pay, normally needs the agreement of employer and employee. The wider policy picture is covered under flexible working.

United States. Under the federal FLSA, overtime is owed to covered, non-exempt employees for hours over 40 in a workweek, a fixed period of 168 hours; averaging hours across two or more weeks is not permitted. Four 10-hour days add up to 40, so the federal rule alone does not trigger overtime. State law can. California, for example, counts overtime after eight hours in a workday, and most of its wage orders handle four 10-hour days through a separate alternative workweek schedule. Check the state where each employee works before you publish a compressed schedule.