To bring in a selective four-day workweek, how do you align work rules, wages and social insurance?

Bottom line first: A selective four-day workweek lets employees who wish choose a three-day weekend, and the extra day off means reworking work rules, wages and social insurance at the same time. In the type that keeps total working hours and adds a day off, a day's scheduled hours exceed eight, so you design it with a variable working-hours system (Labour Standards Act Articles 32-2 and 32-4). Because holidays, working hours and wages are mandatory items in work rules, a change to the work rules (Article 89) is required. If scheduled working days or wages fall, this can affect the occasional revision of the standard monthly remuneration for social insurance (Health Insurance Act Article 43, Employees' Pension Insurance Act Article 23). Subsidies and tax tied to introduction are not covered here; a Shakai Hoken Roumushi handles the work rules and labour-management agreements as an independent business entity.

This page focuses on how to design the increase of scheduled holidays that is a three-day weekend, through work rules, wages and social insurance.

Is a selective four-day workweek just a matter of adding days off?

A selective four-day workweek does not put everyone on a three-day weekend uniformly; it lets employees who wish choose it. It looks like merely adding a day off, but the design changes completely depending on whether the added day is absorbed by working hours or by wages.

Type	Scheduled working hours	Wages	Main issues
Keep-total-hours	Extend a day's scheduled hours to keep the total (e.g. 10 hours × 4 days)	Kept	Over 8 hours a day = a variable working-hours system is the premise
Wage-reduction	Reduce scheduled days and total hours	Reduced in line with hours	Disadvantageous change; social-insurance grade
Wage-maintained	Reduce total hours	Kept	Securing the source of funds; evaluation system

Which type you choose changes how work rules are amended and how premium wages and social insurance are affected. The starting point is to decide whether the added day off is absorbed by working hours, by a wage cut, or by keeping wages.

If total working hours stay the same, what happens to a day's scheduled hours?

If you add a day off while keeping total hours, the same total is spread over fewer days, so a day's scheduled hours grow longer. For example, spreading 40 hours a week over 4 days makes 10 hours a day, exceeding the statutory 8 hours a day (Labour Standards Act Article 32). To avoid this excess becoming overtime, you design it with a variable working-hours system that sets "10 hours a day" in advance.

System	Basis	How it is set	Where it fits
Monthly variable working hours	Labour Standards Act Article 32-2	Set in work rules or a labour-management agreement	When you want to vary working days and holidays within a month
Yearly variable working hours	Labour Standards Act Article 32-4	Conclude a labour-management agreement and file it with the Labour Standards Inspection Office	When you want to allot across a year to match peaks

If you set 10-hour days without a variable working-hours system, the 2 hours over 8 become overtime and trigger premium wages (Labour Standards Act Article 37). Choosing a system is set out in Choosing variable working hours and flextime, and the overtime cap in How far can a 36 Agreement allow overtime. Which unit of variable system fits turns on the share of employees choosing the three-day weekend and the peaks of the business.

Where and how do you change work rules and the labour-management agreement?

Holidays, working hours and wages are all mandatory items in work rules (Labour Standards Act Article 89). When introducing a selective four-day workweek, set the eligible persons, scheduled holidays, scheduled working hours and treatment of wages in the work rules. A worksite constantly employing 10 or more workers has a duty to prepare or change the work rules and file them with the Labour Standards Inspection Office (same Article), hearing the opinion of a majority representative on preparation or change (Article 90).

Document to change	Basis	Content
Work rules	Labour Standards Act Article 89	Set the eligible persons, scheduled holidays, a day's scheduled hours and treatment of wages. File with the Inspection Office if 10+
Labour-management agreement (variable working hours)	Articles 32-2 / 32-4	Monthly can be by work rules; yearly needs an agreement plus filing
Opinion letter	Article 90	Hear the majority representative's opinion on changing the work rules

The Ministry of Health, Labour and Welfare's "Model Work Rules" also has example provisions on holidays, working hours and variable working hours, a starting point for the design. From how many employees work rules are mandatory in the first place is in From how many employees are work rules mandatory, and hourly annual leave, another way to make time off flexible, in Introducing hourly annual leave and the labour-management agreement.

If scheduled working days fall, does it affect premiums or the social-insurance grade?

It can. Where wages are set by the hour or the day, or where a monthly salary is reduced in line with fewer scheduled days, the fixed wage changes. If, from the month the fixed wage changed, the average remuneration over three consecutive months differs by two or more grades from the former standard monthly remuneration, the standard monthly remuneration for social insurance is revised occasionally (Health Insurance Act Article 43, Employees' Pension Insurance Act Article 23). When the standard remuneration falls, future pension and benefits such as injury-and-sickness allowance also fall.

Item	Effect
Occasional revision (notice of monthly amount change)	A fixed-wage change plus a two-grade or more difference in the three-month average = the standard monthly remuneration is revised from the fourth month
Insured status	If scheduled hours/days fall below three-quarters of a regular worker, loss of status is possible (coverage continues if the expanded-coverage requirements for short-hour workers are met)
Premium wages	In the type that extends a day's scheduled hours, overtime premiums arise unless the variable system is designed correctly

The idea of occasional revision of the standard monthly remuneration is in When does the occasional revision of the standard monthly remuneration happen, the three-quarters rule and short-hour workers in Social insurance for short-hour workers and the three-quarters rule, and the course of expanded coverage in How far will the expansion of social-insurance coverage go. Where an employee uses the extra day off for a side job, the aggregation of working hours is set out in Labour management of side and secondary jobs. Exactly which employee drops how many grades turns on how wages are set and the three-month remuneration record, so we do not conclude on the individual case here (unverified).

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If only those who wish take a three-day weekend, is it a disadvantageous change?

The type where wages fall with a three-day weekend can be a disadvantageous change, because it lowers the labour condition of wages. However, if it is applied as a selective system that "those who wish choose for themselves", based on the person's consent, a dispute over a disadvantageous change is less likely to arise. The Labour Contract Act provides that an employer cannot change labour conditions disadvantageously through work rules without the worker's agreement (Article 9), and requires reasonableness for a change of labour conditions by changing work rules (Article 10).

Situation	View
Those who wish choose a three-day weekend (wage cut) themselves	Based on the person's consent = a disadvantageous-change dispute is less likely
Adding the system itself to the work rules	The content of the change must be reasonable (Labour Contract Act Article 10)
Putting everyone uniformly on a three-day weekend (wage cut)	Cannot be lowered without the workers' agreement (Article 9); reasonableness must be examined

Designing it selectively is itself the key to lowering the risk of a disadvantageous change. Even so, the final legal judgement of where to draw the line of eligibility and whether the way consent is obtained is proper turns on individual circumstances, so we do not conclude on the individual case here (unverified). How to align labour conditions including workers after conversion to an open term is in The practice of the open-term conversion rule.

What can 四葉社会保険労務士事務所 do?

What this office takes on is designing a selective four-day workweek safely from the sides of work rules, wages and social insurance.

• Organising which of the keep-total-hours, wage-reduction and wage-maintained types to design
• Designing a variable working-hours system (monthly or yearly) in the type where a day exceeds 8 hours, and preparing the work rules, labour-management agreement and filing
• The change of work rules (eligible persons, scheduled holidays, scheduled hours, treatment of wages) and how to hear the majority representative's opinion
• Confirming the occasional revision and insured status for social insurance arising from changes in scheduled days and wages
• How to obtain consent in a form where those who wish choose, and a design that lowers the risk of a disadvantageous change

Subsidies and tax tied to introduction are not covered in this article; tax is the area of a tax accountant. 四葉社会保険労務士事務所 accepts the preparation of work rules and labour-management agreements as an independent business entity.

Consultations are free of charge. Fees are set out in the fee schedule; see also our services and how a consultation proceeds.

Frequently asked questions

Q. What happens to overtime pay if we go to a three-day weekend?
A. In the type that keeps total hours and extends a day's scheduled hours (e.g. 10 hours × 4 days), the part over 8 hours a day becomes overtime as it stands and triggers premium wages (Labour Standards Act Article 37). To avoid this, you must set a day's scheduled hours in advance with a monthly (Article 32-2) or yearly (Article 32-4) variable working-hours system. A design without the variable system can increase overtime pay.

Q. Where do we change the work rules?
A. Because holidays, working hours and wages are mandatory items in work rules (Labour Standards Act Article 89), set the eligible persons, scheduled holidays, a day's scheduled hours and treatment of wages in the work rules. A worksite constantly with 10 or more has a duty to change them and file them with the Inspection Office, hearing the majority representative's opinion on the change (Article 90). If you use yearly variable working hours, concluding and filing a labour-management agreement is also required.

Q. If wages fall with a three-day weekend, what happens to social insurance?
A. If wages fall so the fixed wage changes, and the three-month average remuneration from that month differs by two or more grades from the former standard monthly remuneration, the standard monthly remuneration is revised occasionally (Health Insurance Act Article 43, Employees' Pension Insurance Act Article 23). When the standard remuneration falls, future pension and injury-and-sickness allowance also fall. If scheduled hours/days fall below three-quarters of a regular worker, insured status can be affected too.

Q. If only those who wish take a three-day weekend, does that avoid a disadvantageous change?
A. If it is a selective system that employees who wish choose for themselves and is applied based on the person's consent, a disadvantageous-change dispute is less likely. The Labour Contract Act provides that an employer cannot change labour conditions disadvantageously through work rules without the worker's agreement (Article 9) and requires reasonableness for a change of work rules (Article 10). A form that lowers everyone's wages uniformly needs agreement or an examination of reasonableness.

Basis for this article

• Labour Standards Act (Act No. 49 of 1947) Article 32 (working hours = 40 a week, 8 a day), Article 32-2 (monthly variable working hours; set by work rules or the like, or a labour-management agreement), Article 32-4 (yearly variable working hours; a labour-management agreement and filing with the administrative authority are required), Article 37 (premium wages for overtime, holiday and late-night work), Article 89 (duty to prepare and file work rules; an employer constantly employing 10 or more workers; holidays, working hours and wages are mandatory items), Article 90 (hearing a majority representative's opinion on preparation or change)
• Labour Contract Act (Act No. 128 of 2007) Article 9 (an employer cannot change labour conditions disadvantageously through work rules without the worker's agreement), Article 10 (a change of labour conditions by changing work rules requires reasonableness of the change)
• Health Insurance Act (Act No. 70 of 1922) Article 43 and Employees' Pension Insurance Act (Act No. 115 of 1954) Article 23 — occasional revision of the standard monthly remuneration (notice of monthly amount change) where, after a fixed-wage change, the average remuneration over three consecutive months differs by two or more grades from the former standard monthly remuneration
• Ministry of Health, Labour and Welfare, "Model Work Rules" — example provisions on holidays, working hours and variable working hours (accessed 1 October 2026); Ministry of Health, Labour and Welfare, introduction and case examples of the "selective four-day workweek" (accessed 1 October 2026)
• Which type to design, how many grades the occasional revision moves, and the final legal judgement on how consent is obtained and the reasonableness of a disadvantageous change turn on how wages are set, the remuneration record and individual circumstances. This article does not conclude on the individual case (unverified)

This article is general information. Individual determinations are made by a qualified professional after a consultation, in light of individual circumstances. 四葉社会保険労務士事務所 can advise on choosing the type of three-day weekend, designing the variable working-hours system and preparing the work rules, labour-management agreement and filing, the change of work rules and hearing the majority representative's opinion, confirming the occasional revision and insured status arising from changes in scheduled days and wages, and how to obtain consent in a form where those who wish choose. Subsidies and tax tied to introduction are not covered here, and tax is the area of a tax accountant. 四葉社会保険労務士事務所 accepts work as an independent business entity. Frequently asked questions are collected in the FAQ. Written by Joji Uramatsu (Shakai Hoken Roumushi, Gyoseishoshi, Registered Real Estate Transaction Specialist).