I have negotiated a four day week twice. I would recommend a four day week to anyone who can afford it. Don't forget that because of tax bands the effective pay cut is less than 20%.
The first time I just straight up asked my boss in a conversation and with a request in writing. I said I was unhappy in my life in general and wanted more time to spend on other things than work. There is legislation in the UK that means that employers must consider these requests and reply with an answer and explanation in a fixed time frame. They accepted and I worked it for about 4 months before other circumstances meant I had to relocate and leave that company.
The job I moved to was a start-up. After a string of executive resignations and engineering team redundancies I was left as the most experienced team member. I had another job offer in hand that I didn't really want but took it to the only remaining senior lead and asked for 4 days (at full pay this time) or I'd leave. They accepted in an informal way rather than modify my contract in this case and just called it "taking a day off when you need it". I would not recommend accepting this in general as it puts you in a vulnerable position for being punished for doing what you thought was the agreed deal. In any case, working 4 days at this job was a disaster because the company was such a mess and I had so little support that I spent my day off and my weekends obsessing about work unhealthily. I ultimately went back to 5 days in a more senior role to try to help right the ship but couldn't take the stress then either so ended up leaving.
I'm now at 5 days again. If I stick my new job out I plan to request 4 days after my probation period ends.
The decision for an employer comes down to retention - do they want to keep you enough to accept 4 days instead of the risk of you leaving? So if you have a manager who can understand your value and represent that to internal decision makers then that's the main key.
The first time I just straight up asked my boss in a conversation and with a request in writing. I said I was unhappy in my life in general and wanted more time to spend on other things than work. There is legislation in the UK that means that employers must consider these requests and reply with an answer and explanation in a fixed time frame. They accepted and I worked it for about 4 months before other circumstances meant I had to relocate and leave that company.
The job I moved to was a start-up. After a string of executive resignations and engineering team redundancies I was left as the most experienced team member. I had another job offer in hand that I didn't really want but took it to the only remaining senior lead and asked for 4 days (at full pay this time) or I'd leave. They accepted in an informal way rather than modify my contract in this case and just called it "taking a day off when you need it". I would not recommend accepting this in general as it puts you in a vulnerable position for being punished for doing what you thought was the agreed deal. In any case, working 4 days at this job was a disaster because the company was such a mess and I had so little support that I spent my day off and my weekends obsessing about work unhealthily. I ultimately went back to 5 days in a more senior role to try to help right the ship but couldn't take the stress then either so ended up leaving.
I'm now at 5 days again. If I stick my new job out I plan to request 4 days after my probation period ends.
The decision for an employer comes down to retention - do they want to keep you enough to accept 4 days instead of the risk of you leaving? So if you have a manager who can understand your value and represent that to internal decision makers then that's the main key.