Social insurance for construction businesses and the special labor-insurance enrollment of a one-person master (hitori-oyakata)

In short: A construction business license requires "appropriate social insurance enrollment" in health insurance, employees' pension and employment insurance (the amended Construction Business Act, in force from 1 October 2020). Meanwhile, a one-person master (hitori-oyakata), who as a rule works without using workers, is not a "worker" under labor insurance, so to receive industrial-accident cover they use the special enrollment for one-person masters (Type 2, Article 35 of the Industrial Accident Compensation Insurance Act) through an association of one-person masters. The enrollment channel and the requirements differ from the special enrollment of a small and medium business owner who hires workers (Type 1, Article 34). This article sorts out the social-insurance duty of a construction business and the special labor-insurance enrollment of a one-person master. Enrollment procedures, work rules and consultation on the association-based procedure are for a Shakai Hoken Roumushi; the construction license application and requirement check are for a Gyoseishoshi (四葉行政書士事務所 — a separate business entity from this office, contracted separately).

"We are taking or renewing a construction license, so we want to put social insurance in order," and "I am a one-person master who works on site — what should I do about industrial-accident cover?" — these are consultations we receive from construction businesses. This page is for businesses that face a construction license and want to arrange social insurance and a one-person master's industrial-accident cover. Confirming an individual enrollment eligibility or a fixed premium amount is done by a qualified professional after a consultation.

Is social insurance enrollment mandatory for a construction license?

Yes. The amended Construction Business Act, in force from 1 October 2020 (amended by Act No. 30 of 2019), added "appropriate social insurance enrollment" as a requirement (a criterion) of the construction license. For both a new application and a renewal, whether you are enrolled in the social insurance you must join is checked. If you have a duty to enroll but are not enrolled, you do not meet the requirement.

"Appropriate social insurance" is decided by the form and scale of the workplace.

Type of workplace	Health insurance	Employees' pension	Employment insurance
Corporation (even with one officer)	Required	Required	Required if you hire workers
Sole proprietor, 5 or more regularly	Required	Required	Required if you hire workers
Sole proprietor, fewer than 5	Exempt (National Health Insurance etc. is fine)	Exempt (National Pension is fine)	Required if you hire workers

Health insurance and employees' pension are compulsory for a corporation even with one officer, and for a sole proprietor with 5 or more workers on a regular basis. A sole proprietor with fewer than 5 is exempt from these two and meets the requirement while staying on National Health Insurance and National Pension. Employment insurance is required once you hire even one worker. Because the duty is judged per workplace, the starting point is to confirm which category your business is in before you prepare the license. Whether you must enroll also relates to the judgment of "worker" status — see where the line between subcontracting and employment lies.

How does a one-person master specially enroll in industrial-accident insurance?

A one-person master is a self-employed person who works, as a rule, without using workers (Article 33, item 3 of the Industrial Accident Compensation Insurance Act). Industrial-accident insurance originally covers the work and commuting injuries of a "worker," so a one-person master, who is not a worker, has no such cover as they are. This is why the special enrollment for one-person masters (Type 2, Article 35 of the same Act) exists.

• You cannot enroll directly as an individual; you apply through an association of one-person masters (a special-enrollment association), which carries out the procedure in a position equivalent to an employer
• You choose the benefit base daily amount that is the basis of cover, from a set range; the higher the daily amount, the higher both the premium and the benefit
• Some construction work by a one-person master requires a health check depending on the actual nature of the work

A one-person master's labor-insurance framework changes if they hire workers. Once they take on workers, they are no longer a one-person master, and a separate procedure for a labor-insurance-applicable business is needed. For the idea of special enrollment when involved with overseas sites, see overseas business trips and overseas assignment are completely different for industrial-accident insurance.

How does a small business owner's special enrollment differ from a one-person master's?

Both are "special enrollment on the business owner's side," but the basis article and the enrollment channel differ. Confusing them stalls the procedure.

	Type 1: small business owner etc.	Type 2: one-person master etc.
Basis	Article 34 (targets are items 1 and 2 of Article 33)	Article 35 (targets are items 3 to 5 of Article 33)
Who can enroll	A small and medium business owner who hires workers, and family workers etc.	A one-person master etc. who as a rule works without using workers
Enrollment channel	Enroll by entrusting labor-insurance affairs to a labor-insurance affairs association	Enroll through an association of one-person masters (special-enrollment association)
Premise	An industrial-accident insurance relationship is established for the workers	Not hiring any workers

The key is whether you hire workers. An owner who hires workers is Type 1 (small business owner etc.), which premises that the industrial-accident relationship is established for the workers, and enrolls through a labor-insurance affairs association. A one-person master who works without hiring workers is Type 2 and enrolls through an association of one-person masters. Why a company with only its president cannot specially enroll as a small business owner is set out in the president gets no industrial-accident benefit — and with one person, no special enrollment either. Even for the same "construction business owner," which system you ride on depends on the reality of employment.

Who should you split the enrollment procedures and the construction license application between?

The social insurance and the license of a construction business divide by qualification. Splitting them at the outset prevents gaps and duplicated work.

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What is done	Whose domain
Enrollment procedures for health insurance, employees' pension and employment insurance; qualification acquisition/loss filings; putting work rules in order; consultation on the one-person master's association-based procedure	Shakai Hoken Roumushi (this office)
Application/renewal of the construction license, requirement check, business-condition review	Gyoseishoshi (四葉行政書士事務所 — a separate business entity from this office; contracted separately)
Registration such as company incorporation or officer change	Judicial scrivener
Tax and closing accounts relating to labor- and social-insurance premiums	Tax accountant

The social-insurance enrollment procedures, the labor-insurance filings and putting work rules in order are the work of a Shakai Hoken Roumushi. The construction license application and requirement check are handled by a Gyoseishoshi. 四葉 has both a Shakai Hoken Roumushi office and a Gyoseishoshi office, but each is a separate business entity, and the contracts, invoices and payment destinations are separate. There are no referral fees exchanged. The duty to create and file work rules arises from ten or more workers on a regular basis (from how many employees are work rules mandatory).

What can 四葉社会保険労務士事務所 do?

四葉社会保険労務士事務所, in Kohinata, Bunkyo City, handles the enrollment procedures for a construction business's health insurance, employees' pension and employment insurance, the annual labor-insurance update, qualification acquisition/loss filings, putting work rules in order, and consultation on a one-person master's association-based procedure. The construction license application itself is handled by a Gyoseishoshi (四葉行政書士事務所 — a separate business entity, contracted separately), and this office takes the social-insurance side. Consultation is free. For fees, see the fee schedule; for frequently asked questions, see the FAQ.

Frequently asked questions

Q. I am a one-person master — is it a problem to work on site without industrial-accident cover?
A. By law, a one-person master's special enrollment is not compulsory. However, prime contractors' sites often require proof of special enrollment, and you may be unable to enter without it. Without special enrollment, an injury during work has no industrial-accident benefit. Whether to enroll and how to choose the benefit base daily amount is arranged by a qualified professional according to the reality.

Q. Can a one-person-president company with no employees specially enroll as a one-person master?
A. In some cases, yes. A company that uses no workers at all cannot join the special enrollment for small and medium-sized business owners (Type 1), because it presupposes that a workers' accident compensation insurance relationship has been established for workers. On the other hand, where a business of a type specified by ministerial ordinance, such as construction, is habitually carried on without using workers, even a corporation's representative may be able to join as a one-person master (Type 2; Article 33, item 3 of the Industrial Accident Compensation Insurance Act) through a one-person masters' association. The treatment differs depending on whether there are officers other than the representative and on the number of days workers are used, so individual eligibility needs to be confirmed with the association you join and the competent Labor Bureau.

Q. If I am a sole proprietor with 4 employees, do I not need health insurance and employees' pension?
A. A sole proprietor with fewer than 5 on a regular basis is exempt from health insurance and employees' pension and meets the construction license requirement on National Health Insurance and National Pension. Employment insurance, however, is required once you hire even one worker. Once you reach 5 or more, health insurance and employees' pension become compulsory, so watch for changes in headcount.

Q. I enrolled in social insurance for the construction license. Do I also need work rules?
A. The duty to create and file work rules arises at a workplace that regularly uses ten or more workers. Under ten, there is no creation/filing duty, but clarifying working conditions is required from the first worker. The license requirement is social-insurance enrollment, not the presence of work rules, but there is meaning in preparing them for on-site labor management.

Sources

• Construction Business Act (Act No. 100 of 1949), Article 7 = criteria for a general construction license. The amendment by Act No. 30 of 2019 (in force from 1 October 2020) added "appropriate social insurance enrollment" as a license requirement via the Construction Business Act Enforcement Regulation
• Industrial Accident Compensation Insurance Act (Act No. 50 of 1947), Article 33 = the targets of special enrollment (items 1 and 2 = small business owners etc., items 3 and 4 = one-person masters etc., item 5 = specified-work engagers, items 6 and 7 = overseas assignees) / Article 34 = special enrollment of small business owners etc. (Type 1) / Article 35 = special enrollment of one-person masters etc. (Type 2) / Article 36 = special enrollment of overseas assignees (Type 3)
• Health Insurance Act (Act No. 70 of 1922) and Employees' Pension Insurance Act (Act No. 115 of 1954) = applicable workplaces (compulsory for a corporation even with one person, and for a sole proprietor with 5 or more; a sole proprietor with fewer than 5 is exempt)
• The making of "appropriate social insurance enrollment" a license requirement (in force from 1 October 2020) and the corporation / sole-proprietor-5-or-more / sole-proprietor-fewer-than-5 distinction are confirmed from the Ministry of Land, Infrastructure, Transport and Tourism's "On social-insurance enrollment measures in construction" and materials published by the Tokyo Metropolitan Bureau of Urban Development (both referenced 22 September 2026)
• The provisions are confirmed from e-Gov Law Search (as of September 2026)

This article does not decide whom to consult. The social- and labor-insurance enrollment procedures, putting work rules in order, and consultation on a one-person master's association-based procedure are the work of a Shakai Hoken Roumushi. The construction license application and requirement check are the work of a Gyoseishoshi (四葉行政書士事務所 — a separate business entity, contracted separately); registration is a judicial scrivener's; tax is a tax accountant's. 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. A judgment on individual circumstances is made by a qualified professional after a consultation. Written by Joji Uramatsu (Shakai Hoken Roumushi, Gyoseishoshi, Registered Real Estate Transaction Specialist).