Social insurance coverage expands from October 2027 to companies with 36 or more employees. Part-time worker requirements and what a company should prepare

In short: For part-time and casual workers, social insurance (health insurance and employees' pension insurance) coverage first depends on whether "both the prescribed weekly working hours and the prescribed monthly working days are at least three-quarters of those of a regular worker." If they are at least three-quarters, the worker is in principle subject to enrollment regardless of company size. For "short-time workers" below three-quarters, the enrollment rules below (20 or more hours a week, not a student, employment expected to exceed two months, and the wage requirement) apply when the workplace meets the company-size requirement.

That company-size requirement will change in October 2027. The range of subject companies will expand from the current "51 or more Employees' Pension Insurance insured persons" to "36 or more." It will then be lowered in stages to 21 or more in October 2029 and 11 or more in October 2032, and in October 2035 the company-size requirement in the expansion of coverage to short-time workers will be abolished. This "number" is not simply the total number of employees; in principle, it is the number of Employees' Pension Insurance insured persons, and for a corporation it is counted across the entire company. In addition, the wage requirement (monthly pay of 88,000 yen or more) is scheduled for abolition in October 2026. What a company should first check is: (1) when it becomes subject, (2) which part-time/casual workers may be covered, (3) explanation to those workers and enrollment procedures, and (4) the insurance-premium burden.

Even if you think "we have 50 or fewer employees, so it doesn't affect us," the company-size requirement will be lowered in stages, so your company could become subject within a few years. This article explains, for business owners who employ part-time/casual workers, especially small and medium-sized company managers, the basics of enrollment decisions for part-time/casual workers, the change in the company-size requirement from October 2027, and what a company should prepare.

Part-time/casual workers' social insurance first depends on the three-quarters rule

Social insurance enrollment for part-time and casual workers is first judged by the following "three-quarters rule."

• Prescribed weekly working hours at least three-quarters of those of a regular worker
• Prescribed monthly working days at least three-quarters of those of a regular worker

A person who meets both is, in principle, subject to health insurance and employees' pension insurance enrollment regardless of company size.

On the other hand, for "short-time workers" below three-quarters, when the workplace meets a certain company-size requirement, the enrollment rules for the expansion of coverage explained in this article (20 or more hours a week, not a student, employment expected to exceed two months, the wage requirement, etc.) apply. The "change in the company-size requirement from October 2027" below concerns the expansion of coverage to these short-time workers.

From October 2027, how does the range of companies subject to social insurance change?

For short-time workers below three-quarters, enrollment requires not only the worker's conditions (20 or more prescribed hours a week, employment period, pay, etc.) but also the "company size" of the workplace. This company-size requirement will be lowered in stages from October 2027.

Period	Company size subject to the requirement (number of Employees' Pension Insurance insured persons)
Currently	51 or more
October 2027	36 or more
October 2029	21 or more
October 2032	11 or more
October 2035	Company-size requirement abolished (size no longer matters in the expansion of coverage to short-time workers)

In other words, companies that are currently "not subject because they have fewer than 51" may become subject in stages from October 2027. It is important to look not only at "whether we are subject now" but also at "when we may become subject."

How is "36 employees" counted?

The company size is not simply the total number of employees. In principle, it is judged by the total number of Employees' Pension Insurance insured persons (short-time workers are in principle not included in this total).

• The concept of "ordinarily" (joji): under current Japan Pension Service guidance, a designated applicable workplace is determined by whether it is expected to have the threshold number or more for six months or more of the year. It is not determined by the number at a single point in time.
• Corporation: judged by adding up the insured persons of all applicable workplaces belonging to the same corporation (same corporate number). Even if there are a head office and branches/sales offices, they are counted as one number for the entire corporation.
• Sole proprietorship: judged by the number of insured persons per applicable workplace.

Therefore, "having 36 employees" does not necessarily mean the company is subject. Conversely, even a company with many part-time/casual workers can become subject if it has the threshold number or more of full-time-equivalent (at least three-quarters of a regular worker) insured persons.

What are the conditions for part-time/casual workers who become subject?

Among short-time workers below three-quarters at a company that meets the company-size requirement, those who meet the following conditions become subject to social insurance enrollment.

• At least 20 hours of prescribed working time per week
• Not a student (those expecting to graduate, evening courses, part-time high schools, or on leave of absence may be exceptionally subject)
• Expected to be employed beyond two months. Even if the initial employment contract is for two months or less, if it is expected, due to renewal or otherwise, that the worker will be employed beyond the initial period, the worker may be subject from the start of the contract. If there was initially no plan for renewal but renewal becomes expected partway, qualification acquisition may be required at the time the expectation arises.
• Prescribed pay of 88,000 yen or more per month (this wage requirement is scheduled for abolition in October 2026)

When the wage requirement is abolished in October 2026, a worker at a company meeting the company-size requirement will become subject regardless of pay if they satisfy "20 or more hours a week, not a student, and employment expected to exceed two months." However, this abolition of the wage requirement is scheduled for October 2026 and is not yet in effect.

Note that, at present, the minimum wage exceeds 1,016 yen per hour in every prefecture, so working 20 or more hours a week at or above the minimum wage would also satisfy the monthly wage requirement of 88,000 yen.

For the basics of enrollment decisions, see what happens to social insurance when you hire someone for short hours. For details of the October 2026 abolition of the wage requirement, see the "1.06 million yen wall" is abolished in October 2026. What a business owner should do.

How does a company identify, and explain to, the affected workers?

When the company-size requirement changes, the practical work a company does roughly follows this flow.

1. Check your company's size: check the number of Employees' Pension Insurance insured persons using the "ordinarily" concept (whether it is expected to be at least the threshold number for six months or more of the year; for a corporation, add up all workplaces; for a sole proprietorship, per workplace).
2. Identify the people who may become subject: separate those who meet the three-quarters rule from short-time workers below three-quarters, and cross-check prescribed working hours, employment period, and student status against the employment contract, work rules, and attendance records.
3. Explain to the workers: explain the timing of enrollment, premiums, and future benefits (employees' pension, injury and sickness allowance, childbirth allowance, etc.) to those who become subject. The Ministry of Health, Labour and Welfare also advises companies to explain in advance and prepare internally.
4. Reflect in notifications and payroll: submit the insured-person acquisition notification, calculate premiums and deduct them from pay, and keep attendance records.

For putting work rules and employment contracts in order, see from how many employees are work rules mandatory. For the choice between outsourcing and in-house payroll, see how much does it cost to entrust payroll to a Shakai Hoken Roumushi and what to ask a Shakai Hoken Roumushi when you want to handle payroll in-house with freee.

How does the insurance-premium burden change? What is the insurance premium adjustment system?

As coverage expands, both the worker and the company bear social insurance premiums. As a mechanism to ease this burden for a certain period, there is the insurance premium adjustment system (Hokenryo Chosei Seido).

In addition to workplaces that newly become subject due to the expansion of coverage from October 2027, the insurance premium adjustment system may also apply to certain workplaces that can newly become voluntarily designated applicable workplaces from October 1, 2026.

The target is insured persons who enroll as short-time workers and whose standard monthly remuneration is 126,000 yen or less. By the business owner temporarily additionally bearing part of the employee's share, the insured person's health insurance and employees' pension insurance premium burden can be reduced for a total of three years. This temporary additional burden is later adjusted, and it is not a mechanism that increases the total amount of premiums ultimately paid by the business owner. The business owner must make the application within two years from the day the workplace became subject to the system.

For details and forms of the insurance premium adjustment system, see the materials published by the Ministry of Health, Labour and Welfare and the Japan Pension Service. For premium estimates and post-enrollment payroll, you can consult a Shakai Hoken Roumushi.

For companies that are not subject now, when do they become subject?

The company-size requirement will be abolished in stages by October 2035. Therefore, rather than thinking "we have 50 or fewer employees, so it doesn't matter," it is necessary to understand at which stage your company's size becomes subject.

Note that the "abolition of the company-size requirement" in October 2035 means that the company-size requirement in the expansion of coverage to short-time workers is abolished. It does not mean that all sole proprietorship workplaces automatically become compulsorily covered workplaces in 2035. For sole proprietorship workplaces, there are separate rules, a 2029 amendment, and transitional measures concerning the scope of compulsory coverage of the workplace itself.

Also, even a company whose number of Employees' Pension Insurance insured persons falls short of the threshold can, by the business owner's application after obtaining certain labor-management agreement, become a "voluntarily designated applicable workplace" in which short-time workers become subject. For the detailed agreement requirements, see the Japan Pension Service guidance.

The rise in the minimum wage also has the effect of increasing the number of people whose prescribed pay reaches 88,000 yen a month. For trends in the minimum wage, see the 2026 minimum wage increase guideline of 55 yen. What a small business should check first.

What should a company ultimately do?

Responding to the regulatory change proceeds in the flow of "follow the news → check primary sources → apply it to your company → reflect it in payroll, attendance, and social insurance procedures." Specifically, start with the following four points.

1. Check your company's size and the date it becomes subject: check the number of Employees' Pension Insurance insured persons (using the "ordinarily" concept; for a corporation, add up all workplaces; for a sole proprietorship, per workplace) and understand at which stage from October 2027 your company becomes subject.
2. Identify the people who may become subject: check those who meet the three-quarters rule and the requirements for short-time workers below three-quarters (20 or more hours a week, employment period, and student status).
3. Explain to workers and prepare internally: explain the enrollment timing, premiums, and benefits, and put the work rules and payroll system in order.
4. Consider using the insurance premium adjustment system: if applicable, consider it in light of the two-year application requirement.

四葉社会保険労務士事務所 can advise on sorting out social insurance enrollment requirements, notifications such as qualification acquisition, labor management, work rules, and the payroll and attendance management system. The preparation of social insurance application documents, submission agency, and administrative agency are organized as the business of a Shakai Hoken Roumushi under Article 2 of the Certified Social Insurance and Labor Consultant Act. Consultation is free. For fees, see the fee schedule.

Frequently asked questions

Q. From October 2027, will our company necessarily become subject?
A. Companies whose number of Employees' Pension Insurance insured persons is "ordinarily" 36 or more (expected to be 36 or more for six months or more of the year; for a corporation, judged across the entire company; for a sole proprietorship, per workplace) become subject. Note that the judgment is based on the number of Employees' Pension Insurance insured persons, not simply the total number of employees.

Q. If we have 36 employees, do all part-timers enroll in social insurance?
A. No. First, those who meet the three-quarters rule are subject regardless of company size, but short-time workers below three-quarters are subject if, in addition to the company-size requirement, they work 20 or more prescribed hours a week, are not a student, and are expected to be employed beyond two months (and, until October 2026, a wage requirement of 88,000 yen or more per month). "36 employees means subject" and "all part-timers enroll" are not correct.

Q. Does the company bear the entire insurance-premium burden?
A. In principle, social insurance premiums are split between the worker and the company. By using the insurance premium adjustment system, the business owner temporarily additionally bears part of the employee's share and can reduce the worker's burden for a total of three years (ultimately, the business owner's total payment does not increase), but check the system requirements for details.

Q. If we have 50 or fewer employees, do we not need to do anything yet?
A. Some companies will not be subject as of October 2027, but the company-size requirement will be lowered in stages in 2029 and 2032, and in October 2035 the company-size requirement in the expansion of coverage to short-time workers will be abolished. Rather than "we are not subject now, so it doesn't matter," we recommend understanding when your company may become subject and putting the work rules and payroll system in order in advance.

Sources

• Three-quarters rule: a person whose prescribed weekly working hours and prescribed monthly working days are at least three-quarters of those of a regular worker is an insured person under health insurance and employees' pension insurance (Japan Pension Service, Japan Health Insurance Association)
• Expansion of health insurance and employees' pension insurance coverage for short-time workers: Japan Pension Service, "Expansion of Health Insurance and Employees' Pension Insurance Coverage for Short-time Workers" (updated April 17, 2026). In principle, a designated applicable workplace is one with 51 or more Employees' Pension Insurance insured persons in total (excluding short-time workers), and this will expand to 36 or more from October 2027.
• Staged reduction of the company-size requirement: October 2027: 36 or more → October 2029: 21 or more → October 2032: 11 or more → October 2035: company-size requirement in the expansion of coverage to short-time workers abolished (materials published by the Ministry of Health, Labour and Welfare and the Japan Pension Service; please check the implementation dates each time).
• The "ordinarily" concept: a designated applicable workplace is determined by whether it is expected to have the threshold number or more for six months or more of the year (Japan Pension Service).
• Judgment of company size: for a corporation, the total number of insured persons of all applicable workplaces belonging to the same corporation; for a sole proprietorship, per applicable workplace (Japan Pension Service).
• Enrollment requirements for short-time workers: 20 or more prescribed hours a week / not a student / expected to be employed beyond two months / prescribed pay of 88,000 yen or more per month (the wage requirement is scheduled for abolition in October 2026) (Japan Pension Service).
• Insurance premium adjustment system: applies to workplaces newly subject due to the expansion of coverage from October 2027, and to certain workplaces that can newly become voluntarily designated applicable workplaces from October 1, 2026. For insured persons with a standard monthly remuneration of 126,000 yen or less, the business owner temporarily additionally bears part of the employee's share and reduces the worker's burden for a total of three years (later adjusted; the business owner's total payment does not increase). Application within two years from the day of becoming subject (Japan Pension Service, "Guide to the Insurance Premium Adjustment System," updated April 1, 2026).
• Voluntarily designated applicable workplace: a workplace can become a subject workplace by the business owner's application after obtaining certain labor-management agreement (Japan Pension Service).
• Business of a Shakai Hoken Roumushi: Article 2 of the Certified Social Insurance and Labor Consultant Act.

This article does not decide whom to consult. 四葉社会保険労務士事務所 can advise on sorting out social insurance enrollment requirements, notifications such as qualification acquisition, labor management, work rules, and the payroll and attendance management system. Tax matters are the domain of a tax accountant. For fees when consulting 四葉社会保険労務士事務所, see the fee schedule; for frequently asked questions, see the FAQ.

This article is general information. Whether the system applies and individual enrollment decisions are made by a qualified professional after a consultation, in light of the latest primary sources (the Ministry of Health, Labour and Welfare, the Japan Pension Service, etc.) and individual circumstances. Written by Joji Uramatsu (Shakai Hoken Roumushi, Gyoseishoshi, Registered Real Estate Transaction Specialist).