How to Start a Detective (Investigation) Business: Notification, Office Requirements and Disqualifications under the Detective Business Act

In short: a detective business is not a licensing system but a notification system. Under Article 4 of the Act on Proper Control of Detective Business (the Detective Business Act), before you begin operating you submit, per office, a detective-business commencement notification to the public safety commission with jurisdiction over the location of that office (via the crime-prevention section of the police station with jurisdiction). There is no notification fee. The detective-business notification certificate formerly issued was abolished by the revision in force on 1 April 2024 (Reiwa 6) and replaced by displaying at the office a sign showing that notification has been made (Article 12). The disqualifications that bar a notification are set in Article 3: a person who has been declared bankrupt and has not been restored, a person who has not passed five years since finishing a sentence of imprisonment or above, an organized-crime-group member, and, for a corporation, where an officer falls under these. Lending your own name so that another operates a detective business is prohibited by Article 5, and operating without notification or name-lending carries imprisonment up to six months or a fine up to 300,000 yen. This article is general information and does not make the final judgment on whether a given notification will be accepted. The administrative scrivener of the Yotsuba group handles, as an independent business, support for preparing the detective-business commencement notification and submitting it to the public safety commission. Illegal and dispute matters such as defamation, invasion of privacy and breach of the Anti-Stalking Act in connection with an investigation are for a lawyer; searching for and leasing the property used as an office is for a real-estate agent, a separate business (our company); each is contracted separately. Our office receives no referral fee from any professional.

Is a detective business a licensing or a notification system, and what must you submit before starting?

A detective business is not a "licensing system" where you start after obtaining a licence, but a "notification system" where you notify before you begin. Article 4 of the Act on Proper Control of Detective Business (the Detective Business Act; Act No. 60 of 2006, in force 1 June 2007 (Reiwa, i.e. Heisei 19)) provides that a person who intends to operate a detective business must, before the day operating begins, submit a notification per office to the public safety commission with jurisdiction over the location of that office. In practice it is submitted via the crime-prevention section of the police station with jurisdiction over the office.

Item	Content (Detective Business Act)
System	Notification system (not licensing)
Where	The public safety commission with jurisdiction over the office (via the crime-prevention section of the police station)
When	Before the day operating begins (Article 4(1))
Unit	Per office
Fee	None
Name-lending	Prohibited (Article 5)

"Detective business affairs" here means affairs where, on request of another, with the aim of gathering information on the whereabouts or conduct of a specified person, you carry out an on-site investigation by interviews, tailing, stakeouts and similar methods and report the result to the requester (Article 2(1)). Work done solely on request of a news organization for its reporting is excluded from a detective business (Article 2(2)). Support for preparing and submitting the notification is also covered in our Permit and Licensing services.

What are the "disqualifications" that bar a detective-business notification?

Article 3 of the Detective Business Act sets disqualifications, providing that a person falling under any of the following may not operate a detective business. Before notification, you check that you (or, for a corporation, an officer) do not fall under them.

Item	Disqualification (Article 3)
Item 1	A person who has been declared bankrupt and has not been restored
Item 2	A person who has not passed five years since finishing a sentence of imprisonment or above, or a fine for violating this Act
Item 3	A person who, within the last five years, violated a disposition under Article 15 (suspension/abolition order)
Item 4	An organized-crime-group member, or one not five years past ceasing to be one
Item 5	A person who, due to a mental or physical disorder, cannot properly perform detective-business affairs, as prescribed by Cabinet Office Order
Item 6	A minor without the same capacity as an adult regarding the business, whose legal representative falls under Items 1–5 or Item 7
Item 7	A corporation an officer of which falls under any of Items 1–5

By the 2022 (Reiwa 4) revision of the Penal Code and related acts, imprisonment with and without work was unified into "imprisonment" (koukinkei), in force from 1 June 2025 (Reiwa 7), so the text reads "a sentence of imprisonment or above." The final assessment of whether a disqualification applies is a field for the public safety commission; an administrative scrivener does not guarantee acceptance on your behalf.

What requirements and display duties apply to an office or home-based start-up?

The Detective Business Act has no building structure or facility standard like that for restaurant business, but it requires notification per office and the display of a sign showing that notification has been made. The former notification certificate was abolished by the revision in force on 1 April 2024 (Reiwa 6) (review of the notification procedure) and changed to a method where the operator itself prepares and displays a sign in a conspicuous place at the office (Article 12).

Category	Content
Office	Notification is required per office; a home may be the office (jurisdiction follows the office location)
Sign	Display at a conspicuous place a sign showing notification was made (the old certificate is abolished)
Employee roster	Keep a roster per office (Article 12)
Education	Education so employees perform detective-business affairs properly (Article 11)

The sign states the name of the public safety commission that received the notification, the acceptance number of the notification, the date of notification, the trade name/name, and the name and location of the office. Because the format and instructions are shown by each prefectural police, you confirm the latest content on the jurisdiction's official page before preparing it. Where you lease a property to start up, searching for and leasing the property is a field for a real-estate agent, a separate business (our company), and you may use our real-estate consultation desk. For how engagement proceeds, see our Engagement Flow.

What are detective-business operators required to do in the important-matters statement and contract documents?

In contracting with a requester, a detective-business operator is required both to deliver a document before the contract and to deliver a document after the contract (Article 8). In addition, it must receive from the requester a document stating that the result of the investigation will not be used for an unlawful purpose such as a crime or discrimination (Article 7).

Stage	Basis	Main items
Before the contract (explaining important matters)	Article 8(1)	Trade name/address, the public safety commission notified, matters on confidentiality, content of affairs, whether there is subcontracting, approximate consideration and timing of payment, rescission, disposal of materials
After the contract (clarifying contents)	Article 8(2)	Name of the person in charge and contract date, content/period/method of investigation, method/deadline of the report, amount/timing/method of consideration, provisions on rescission and disposal of materials
Document from the requester	Article 7	Confirmation that the result will not be used for an unlawful purpose

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In performing detective-business affairs, the operator must not infringe individual rights and interests, such as by harming the peace of people's lives, and this Act does not make lawful acts that are prohibited or restricted by other laws (Article 6). Also, subcontracting the whole or part of detective-business affairs to a person who is not a detective-business operator is prohibited, and the operator must not perform the affairs once it knows the result will be used for an unlawful act (Article 9). A guide to our fees is set separately in our Fee Schedule.

What penalties and risks come with failing to notify or lending your name?

Operating a detective business without notifying (operating without notification) and lending your own name so that another operates a detective business (name-lending) carry penalties. Name-lending is expressly prohibited by Article 5, and both operating without notification and name-lending are subject to imprisonment up to six months or a fine up to 300,000 yen (Article 18).

Act	Basis	Penalty
Operating a detective business without notification	Violation of Article 4(1)	Imprisonment up to six months or a fine up to 300,000 yen (Article 18)
Name-lending	Violation of Article 5	Imprisonment up to six months or a fine up to 300,000 yen (Article 18)
Breach of operating rules, false notification, etc.	Each provision	May be subject to a suspension/abolition order (Article 15) or penalties

If you notify without checking the disqualifications, you may later become subject to a disposition. Where you run other businesses such as an antiques dealer in parallel, because the governing law and supervising authority differ, you check them separately. The antiques dealer is organised in Office requirements for an antiques dealer permit and the security business in Requirements, disqualifications and training for security-business accreditation. A major difference is that a security business is an "accreditation," whereas a detective business is a "notification."

When an investigation may exceed the lawful scope, who should it be referred to?

Even with a detective-business notification, if tailing, stakeouts or interviews go too far, they may touch the Act on Regulation of Stalking (the Anti-Stalking Act), defamation or invasion of privacy. These are illegal and dispute matters, outside the scope an administrative scrivener handles. The basis is that each professional involved contracts as an independent business, separately.

Who to ask	Main role
Administrative scrivener (our office)	Support for preparing the detective-business commencement notification and submitting it; organising the check of disqualifications
Lawyer	Response to illegal/dispute matters such as Anti-Stalking Act violation, defamation, invasion of privacy; the final legal judgment
Real-estate agent (our company, a separate business)	Searching for and leasing the property used as an office
Public safety commission / police	Acceptance of the notification; guidance on signs, rosters, etc.

Work where tailing or stakeouts may exceed the lawful scope, and investigations suspected to be for an unlawful purpose, are not handled by our office. Our office contracts with each professional as an independent business, and we receive no referral fee from one another. The final judgment on acceptance or lawfulness is made by a qualified professional or the public safety commission after a meeting.

FAQ

Q. Do you start a detective business after obtaining a licence?
A. No. A detective business is not a licensing system but a notification system. Under Article 4 of the Detective Business Act, before the day operating begins you submit a notification, per office, to the public safety commission with jurisdiction over the location (via the crime-prevention section of the police station). There is no notification fee. It is not a system of waiting for a licence screening, but not falling under the disqualifications and performing duties such as document delivery are preconditions.

Q. Can I start up using my home as the office?
A. You must notify per office, but using your home as the office is itself possible. Jurisdiction is decided by the office location. You must display a sign showing notification was made in a conspicuous place at the office and keep an employee roster (Article 12). The former detective-business notification certificate was abolished by the revision in force on 1 April 2024 (Reiwa 6) and changed to displaying a sign.

Q. What happens if I start a detective business without notifying?
A. A person who operates a detective business without notification is subject to imprisonment up to six months or a fine up to 300,000 yen (Article 18). Name-lending, where you let another operate under your name, is also prohibited by Article 5 and subject to the same penalty. The notification must be completed before the day operating begins.

Q. How far can an administrative scrivener handle?
A. An administrative scrivener handles, as an independent business, support for preparing the detective-business commencement notification and submitting it to the public safety commission, and organising the check of disqualifications. Response to Anti-Stalking Act violation, defamation or invasion of privacy where tailing or stakeouts go too far is a field for a lawyer, and the office property and lease are a field for a real-estate agent, a separate business, each contracted separately.

Sources (Primary Information)

• e-Gov Law Search / National Police Agency, "Act on Proper Control of Detective Business" (Act No. 60 of 2006, in force 1 June 2007 (Heisei 19)), Article 2 (definitions of detective-business affairs and detective business), Article 3 (disqualifications: a person declared bankrupt and not restored; not five years past finishing imprisonment or above, etc.; an organized-crime-group member; mental/physical disorder; a minor; a corporation's officer), Article 4 (notification to the public safety commission per office, before the day operating begins), Article 5 (prohibition of name-lending), Article 6 (principles of performing affairs), Article 7 (receiving a document from the requester), Article 8 (explaining important matters and delivering a document before the contract; delivering a document after the contract), Article 9 (restriction on subcontracting), Article 12 (employee roster and sign), Article 18 (penalties for operating without notification and name-lending = imprisonment up to six months or a fine up to 300,000 yen) (accessed 2026-10-17)
• Prefectural police, "On the partial revision of the Detective Business Act" (in force 1 April 2024 (Reiwa 6): abolition of the detective-business notification certificate [former document under Article 4(3)] and shift to displaying a sign; items/format of the sign; notification before the day operating begins, via the crime-prevention section of the police station with jurisdiction over the office; no notification fee) (accessed 2026-10-17)
• e-Gov Law Search / National Police Agency, "Act on Regulation of Stalking" (a law that may be relevant where an investigation exceeds the lawful scope; the individual lawfulness is a field for a lawyer or investigative authorities) (accessed 2026-10-17)

This article is general information and does not make the final judgment on whether a given notification will be accepted or whether a given investigation is lawful. A detective business is a notification system, with duties such as checking disqualifications and delivering documents. Support for preparing the detective-business commencement notification and submitting it is handled by the administrative scrivener of the Yotsuba group as an independent business; response to illegal and dispute matters such as Anti-Stalking Act violation, defamation and invasion of privacy is by a lawyer; and searching for and leasing the property used as an office is by Yotsuba Real Estate Co., Ltd., a separate business, each contracted separately. Our office receives no referral fee. We do not handle work where tailing, stakeouts, etc. exceed the lawful scope, or requests suspected of an unlawful purpose. Individual judgements are made by a qualified professional or the public safety commission after a meeting. Written by Joji Uramatsu, administrative scrivener and licensed real estate broker.