In a UK wide six month trial of a four-day working week, 56 of the 61 participating companies intend to continue this arrangement. The study, which ran for six months from June 2022, has been subject to debate, but what are the legal ramifications that employers need to consider before instituting this arrangement?

Impact on part-time workers

Employers need to examine carefully the position of part-time workers. If an employee is already working four days a week, with a pro-rated salary, there are a few ways this could be handled.

One option would be to reduce the part-time worker’s week by a proportionate amount and retain their level of pay. 

They would receive 100 per cent of their salary despite a reduction in hours, putting them in the same position as the other employees.

Employers will need to assess whether the part-time role could be carried out effectively over 3.2 days. 


Another option would be simply to increase the pay of the part-time workers to a full-time salary, but keep their hours the same. 

This may be difficult from an employee relations standpoint as it places part-time workers at an advantage. 

They would receive the salary of an employee who would otherwise work five days a week but are only expected to do four days’ worth of work – as opposed to squeezing five days’ worth of work into four days.

The danger in this approach is the potential risk of discrimination. Part-time workers would be denied the opportunity to reduce their hours and retain their pay which may lead to a successful part-time worker discrimination claim. 

Consider the common reasons why employees need to work part time: childcare responsibilities and health concerns. Indirect discrimination can occur when a policy applies to all employees but has a negative impact on those who have a protected characteristic. 

Such a claim may be viable if an employee, who has already demonstrated their need to work reduced hours because of a protected characteristic, does not qualify to take part in a company wide scheme to reduce hours spent at work. 

Trial period 

Employers contemplating a four-day week should initially do so on a trial basis. Practically speaking this would involve issuing employees with a temporary contract variation reducing their working days and stating that the change is temporary and would be reviewed after a set period of time. 

Remember that any permanent change needs to be done by agreement, and employees are unlikely to agree to increase their hours again. 

Other issues

Employees will need to be made aware that their annual holiday allowance will reduce by 20 per cent.

If employees are expected to cover for their colleagues on their respective days off it is possible this would negate the stress relief impact a four-day week has been shown to have. 

Additionally, any expectations of contact on the employee’s day off should be made clear. Thought will need to be given to this in respect of checking emails or answering calls from clients. 


The results of the study seem positive, but employers need to think these issues through carefully before implementing this work pattern.

Natalia Milne is legal manager at Navigator Employment Law