Switching social and labour insurance when incorporating a sole proprietorship — moving to compulsory coverage and employee procedures

Bottom line first: When a sole proprietorship incorporates, social insurance (health insurance and employees' pension) becomes compulsory regardless of the number of employees, because a corporate place of business that regularly uses employees is a covered workplace (Health Insurance Act Article 3(3), Employees' Pension Insurance Act Article 6), unlike a sole proprietorship that was voluntarily covered below five regular employees. After incorporation you file the new-coverage notification and the acquisition-of-insured-status notifications within five days of the triggering fact at the Pension Office (Pension Service guidance), and review the labour-insurance and employment-insurance filings. Registration of the company is a Shiho Shoshi's area, and the transfer of assets and consumption/income tax a tax accountant's, each contracted separately as an independent business entity.

This page focuses on the labour side specific to incorporation: the move from voluntary to compulsory social-insurance coverage, the change of business operator for labour and employment insurance, and switching employees' insured status. The registration itself is a Shiho Shoshi's area and the tax a tax accountant's.

Why does social insurance become compulsory on incorporation?

A corporate place of business is a covered workplace for health insurance and employees' pension if it regularly uses employees (even just the representative, where a using relationship exists) (Health Insurance Act Article 3(3), Employees' Pension Insurance Act Article 6). A sole proprietorship, by contrast, was compulsorily covered only where it regularly used five or more employees in certain industries, and below five or in a non-covered industry it was voluntarily covered (by employee consent and approval; Health Insurance Act Article 31, Employees' Pension Insurance Act Article 10). Incorporation is the move from that voluntary state to compulsory coverage regardless of headcount.

Form of business	Social-insurance coverage
Corporation (kabushiki kaisha, godo kaisha, etc.)	Compulsory regardless of headcount if it regularly uses employees (Health Insurance Act Article 3(3), Employees' Pension Insurance Act Article 6)
Sole proprietorship, certain industries, 5+ regular employees	Compulsory
Sole proprietorship, below 5 or non-covered industry	Voluntary (consent and approval; Health Insurance Act Article 31, Employees' Pension Insurance Act Article 10)

The point is that at the moment of incorporation the company newly becomes a covered workplace, regardless of whether the sole proprietorship had been in social insurance. The deadlines for a newly established company are in Deadlines for social and labour insurance on company formation; the entry concept is common with incorporation.

When do you file the new-coverage and acquisition-of-status notifications?

When the company becomes a covered workplace (when the fact of incorporation occurs), you file the health-insurance and employees'-pension new-coverage notification within five days of the triggering fact, together with an acquisition-of-insured-status notification for each employee. The filing goes to the competent Pension Office or Administrative Centre (Japan Pension Service guidance; accessed 29 October 2026).

Notification	Unit	Deadline guide
New-coverage notification	Workplace	Within 5 days of the triggering fact (Pension Service guidance)
Acquisition-of-insured-status notification	Each employee	Within 5 days of the triggering fact (Pension Service guidance)
Health-insurance dependant (change) notification	Each insured with dependants	Together with the acquisition notification

Attachments such as the company's certificate of registered matters vary with the workplace's situation. The specific forms, attachments and filing methods vary by insurer and jurisdiction, so check the latest Pension Service / Pension Office guidance just before filing (unverified). Where short-hour employees become insured (three-quarters or more of a regular worker, etc.) is set out in From what point do short-hour employees enter social insurance.

What filings are needed for labour and employment insurance when the operator changes?

Labour insurance (workers' accident and employment insurance) is in principle already established if you employed workers as a sole proprietor. Because incorporation changes the operator from an "individual" to a "corporation", you review the labour- and employment-insurance filings. Where a new insurance relationship is established, the establishment notification is due within ten days from the day after the day of establishment (Act on Collection of Labour Insurance Premiums). For employment insurance, filings to Hello Work on the workplace setup and the insured are needed.

Insurance	Likely filing
Labour insurance (premium collection for accident/employment)	Establishment notification, etc. (within 10 days from the day after establishment; Act on Collection of Labour Insurance Premiums)
Employment insurance	Covered-workplace setup notification, filings on the insured (Hello Work)

Whether incorporation is treated for labour insurance as "dissolution of the sole proprietorship plus new establishment of the corporation" or as "a change of operator" depends on how the continuity of the business is viewed. Which procedure applies, and how the insured number is carried over, is premised on checking with the competent Labour Bureau, Labour Standards Inspection Office and Hello Work, and is not concluded here (unverified).

How does coverage switch when you move employees from the sole proprietorship to the corporation?

An employee not in social insurance under the sole proprietorship switches, through acquiring insured status at the corporation, from National Health Insurance and the National Pension to health insurance and employees' pension. One already in social insurance loses status at the sole proprietorship's workplace and acquires it at the corporation's — a transfer. An employment-insurance insured number is one per person and is in principle carried over even when the workplace changes.

Employee's situation	What switches
Not in social insurance under the sole proprietorship	Acquires status at the corporation (National Health Insurance/National Pension → health insurance/employees' pension)
Already in social insurance under the sole proprietorship	Loss at the old workplace and acquisition at the corporation — a transfer
Employment-insurance insured	The insured number is one per person; in principle carried over even if the workplace changes

The timing of wages, the standard monthly remuneration and the start of premium deduction is designed to the acquisition date and the wage closing/payment. Work rules are often reviewed when carried from the sole proprietorship to the corporation; from how many employees they are mandatory is in From how many employees are work rules mandatory, and the labour side of business succession in Business succession and labour when a sole proprietor dies.

What disadvantages arise if you get the timing of the switch wrong?

If you became a covered workplace on incorporation but the filing is late, social-insurance premiums may be charged retroactively to the time of establishment. The double burden with, and adjustment against, National Health Insurance and the National Pension in the interim, and the treatment of the standard remuneration where a bonus or pay rise falls in between, make later sorting complex. Designing at the outset the order of registration, bank account, start of wage payment, and the social/labour-insurance filings helps avoid these disadvantages.

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Easy mistake	Possible disadvantage
Late new-coverage/acquisition notification	Retroactive premium charge; adjustment of the double burden with National Health Insurance/National Pension
Timing gap in employees' loss/acquisition	Gap in insurance card; missed dependant procedure
Missing labour-insurance establishment/change notification	Premium settlement/delay; defects in subsidy-eligibility checks

The scope of retroactivity and the specifics of settlement vary by insurer, jurisdiction and individual circumstances, so this stays at a general caution (unverified). The final treatment is confirmed with the Pension Office and Labour Bureau, and designed by a qualified professional.

Who should you consult about the incorporation procedures?

Incorporation spans several professionals' areas. What a Shakai Hoken Roumushi handles is the social- and labour-insurance filings and labour design; the registration and tax are handled by others.

Procedure	In charge
Company-formation registration, officer-change registration	Shiho Shoshi (a business entity independent of this office)
Transfer of assets/liabilities, consumption/income and other incorporation tax	Tax accountant (a business entity independent of this office)
Social- and labour-insurance filings, transfer of employees' status, preparing work rules and wage rules	Shakai Hoken Roumushi (四葉社会保険労務士事務所)

四葉社会保険労務士事務所 accepts labour work as an independent business entity, and where another professional such as a Shiho Shoshi or tax accountant is needed, we introduce them under a contract you conclude directly, separately. This office takes no referral fee.

What can 四葉社会保険労務士事務所 do?

What this office takes on is the design of labour so that, on incorporation, social and labour insurance are switched at the right time and no retroactive premiums or gaps in status arise.

• Preparing and filing the new-coverage, acquisition-of-status and dependant notifications (arranging the five-day timing from the triggering fact)
• Reviewing the labour- and employment-insurance filings on the operator change (including confirmation with the competent office)
• The transfer of employees' loss/acquisition of status and the design of wages, standard monthly remuneration and premium-deduction start
• Preparing work rules, wage rules, notice of working conditions and working-hour management as a corporation

The registration is a Shiho Shoshi's area and the incorporation tax a tax accountant's. 四葉社会保険労務士事務所 accepts work as an independent business entity, and where another professional is needed, we introduce them under a contract you conclude directly, separately. There is no referral fee.

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. Must you enter social insurance on incorporation even with few employees?
A. Yes. A corporate place of business that regularly uses employees is a covered workplace for health insurance and employees' pension regardless of headcount (Health Insurance Act Article 3(3), Employees' Pension Insurance Act Article 6). Even the representative alone becomes insured if they receive remuneration from the corporation and a using relationship exists. This differs from a sole proprietorship that was voluntarily covered below five regular employees.

Q. By when do you file the social-insurance notifications?
A. When the company becomes a covered workplace, you file the new-coverage notification and the acquisition-of-insured-status notification within five days of the triggering fact, to the competent Pension Office or Administrative Centre (Japan Pension Service guidance). Attachments such as the certificate of registered matters vary with the workplace. Check the latest guidance for the specific forms and filing method just before filing.

Q. Are labour- and employment-insurance procedures also needed?
A. Yes. Because incorporation changes the operator from individual to corporation, you review the labour- and employment-insurance filings. Where a new insurance relationship is established, the establishment notification is due within ten days from the day after establishment (Act on Collection of Labour Insurance Premiums). Whether it is dissolution-plus-new-establishment or a change of operator, and how the insured number carries over, is premised on checking with the competent Labour Bureau and Hello Work.

Q. What happens if the filing is late?
A. Social-insurance premiums may be charged retroactively to the time of establishment, or an adjustment of the double burden with National Health Insurance and the National Pension may arise. A timing gap in employees' loss/acquisition of status can also cause a gap in the insurance card or a missed dependant procedure. We recommend designing at the outset the order of registration, start of wage payment and the social/labour-insurance filings.

Basis for this article

• Health Insurance Act (Act No. 70 of 1922) Article 3(3) (definition of a covered workplace; a corporate place of business regularly using employees is compulsory, a sole proprietorship in certain industries with 5+ regular employees), Article 31 (approval of a voluntarily covered workplace)
• Employees' Pension Insurance Act (Act No. 115 of 1954) Article 6 (covered workplace; a corporate place of business regularly using employees is compulsory, a sole proprietorship in certain industries with 5+ regular employees), Article 10 (approval of a voluntarily covered workplace)
• Act on Collection, etc. of Insurance Premiums of Labour Insurance (Act No. 84 of 1969) — establishment of the insurance relationship and its notification (within ten days from the day after the day of establishment as a guide)
• Japan Pension Service, "New-coverage procedure" and "Acquisition-of-insured-status notification" guidance — the new-coverage and acquisition notifications are filed within five days of the triggering fact to the Pension Office (Administrative Centre) (accessed 29 October 2026)
• The specific forms and attachments for new coverage/acquisition, whether incorporation is "dissolution plus new establishment" or "a change of operator" for labour insurance, the carry-over of the insured number, and the scope of retroactive premiums vary by insurer, jurisdiction and individual circumstances. The final treatment is premised on checking with the Pension Office, Labour Bureau and Hello Work, and 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 preparing and filing the new-coverage and acquisition-of-status notifications on incorporation, reviewing the labour- and employment-insurance operator-change filings, the transfer of employees' status and the design of wages, standard remuneration and premium deduction, and preparing work rules and wage rules as a corporation. The registration is handled by a Shiho Shoshi and the incorporation tax by a tax accountant. 四葉社会保険労務士事務所 accepts work as an independent business entity, and where another professional is needed, we introduce them under a contract you conclude directly, separately; there is no referral fee. Frequently asked questions are collected in the FAQ. Written by Joji Uramatsu (Shakai Hoken Roumushi, Gyoseishoshi, Registered Real Estate Transaction Specialist).