Preparing for the 4-Day Week: A Practical Checklist for HR Departments in the UK

The UK is now officially moving to a four-day work week. Under the Employment Rights Act 2025, employees can request flexible working arrangements like the 4-day week from their first day of employment. This shift puts HR departments in a key role as the way we work evolves.

According to the World Economic Forum, more than 2.7 million UK workers, nearly 11% of the workforce, were already working a four-day week in 2025.

As this trend gains traction, many companies investigate what a 4-day work week looks like in different countries for guidance. Iceland, Japan, and Portugal were early adopters whose trials produced strong outcomes. The UK is approaching it closely, and many workplaces are making similar changes.

This shift involves more than just giving staff a long weekend. It requires major changes in how companies operate, careful planning, clear updates to policies, and strong ways to measure success.

Execution is crucial. When done well, it builds trust and helps keep talented employees. When done poorly, it creates confusion, lowers service quality, and puts HR in a difficult legal position.

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A Practical Checklist for UK’s HR Teams

Here are some practical checklist items for UK’s HR teams should tick:

Understand the Legal Position First

The UK did not have a four-day workweek. However, employees now have stronger rights to ask for flexible working arrangements.

From their first day, employees may request a change. Employers must reply within two months if they deny the request. They must also provide a valid business reason for any denial.

A 2025 CIPD report shows that 45% of UK employees would work a four-day week for the same pay. This highlights the high volume of requests HR teams should prepare to handle.

To manage this demand fairly, HR teams must keep clear records of their decisions. They should clearly explain their reasons when approving or declining a request. This reasoning must be consistent and free from discrimination.

Choose the Right Working Model

Before updating any contract, choose the model that works best for your organisation.

100-80-100 Model

The first option is the 100-80-100 model. When employees and managers ask what a 4-day work week in practice looks like, this is the model commonly described. Workers earn 100% of their pay for working 80% of their hours, provided they meet 100% of their goals. This approach focuses on output instead of time and relies on clear performance guidelines and goals.

Compressed Hours Model

The second option is the compressed hours model. Employees work their full hours over four days instead of five. For example, a 37.5-hour week would be divided into four days of just over nine hours each. Pay stays the same. This model is easier to manage but requires careful monitoring to prevent fatigue by Wednesday afternoon.

Update Contracts and Holiday Entitlements

If you change your working hours, HR teams must update employment contracts. Verbal contracts are not legally binding. Both parties must sign a new contract before changes take effect.

Payroll teams will also need clear guidance on how to work out 4 day week salary levels appropriately, particularly where workers shift from 5 to 4 mid-year. For the 100-80-100 model, salary remains the same. The same goes for compressed hours. If there is a reduction in agreed hours, salary must be adjusted based on the new hours and noted in the revised contract.

Holiday entitlement also needs to be recalculated. In the UK, the statutory entitlement is 5.6 weeks. For someone working four days a week, this equals 22.4 days instead of 28. Special care is needed for bank holidays. If a bank holiday falls on an employee’s day off, HR must decide whether to offer an extra day off or include it in the annual leave. Both options are acceptable, but they must be applied consistently for all employees.

Run a Structured Trial Period

Switching permanently from day one is risky. A trial period of three to six months allows the organisation to gather real data. This avoids making premature permanent changes.

Part of running a successful trial is knowing how to schedule a 4-day work week across teams and departments. Not every team works the same way. Teams that interact with customers may require different days off to ensure coverage. Back-office teams can adjust their schedules more easily. Mapping each team’s workload before the trial starts helps avoid the confusion that can disrupt the operational plans.

Before the trial ends, decide what achievement looks like. Measure client satisfaction, project delivery times, employee absenteeism, and team productivity. Create a simple feedback system for weekly updates on service quality. A short and anonymous survey provides HR with the necessary data to make a fair final decision.

Redesign Workflows Before Cutting Hours

Removing a workday without changing how tasks are done can instantly lead to lower productivity. HR should work with team leaders to establish new habits before the trial begins.

First, reduce meeting times. Establish a rule: if there’s no agenda, the meeting does not happen. Keep most sessions under 25 minutes. Next, motivate teams to dedicate two to three hours daily for focused work. Turn off messaging apps and email checks during these blocks to recover lost hours.

For a closer look at what structural adjustments set successful transitions apart from failed ones, explore this practical guide on executing a four-day workweek, which offers a useful breakdown.

Create a Guide to the Day Off

This step is easy to miss, but it’s key. Many employees, especially those who work hard, may feel uncomfortable taking an extra day off. If left to their own devices, they might check emails and tackle small tasks instead of truly resting.

Understanding how a 4-day work week improves mental health is the first start. Rest helps lower stress and anxiety, allowing the brain to recover between workdays. Employees who take breaks return more focused, sharper, and engaged.

HR should create a short, practical guide that encourages employees to use their days for actual:

• Rest
• Movement
• Creativity, or
• Family time

A well-rested employee on Tuesday morning adds more value than an exhausted one struggling through Friday afternoon.

Conclusion

Switching to a four-day workweek is a big change in how an organisation operates, not just a simple policy update. HR teams that have clear plans, update agreements, run organised trials, and redesign workflows are more likely to succeed.

Success should be measured by output and productivity, not by hours spent at a desk. By planning carefully and tracking results honestly, organisations can let the outcome speak for itself.

If you’re rethinking how your workforce operates beyond hours alone, take a look at our practical guide for HR teams navigating remote and hybrid work.