Responding to a patent infringement complaint or a petition for a provisional disposition (interim injunction) in Japan

What a company should first check after receiving a complaint or a petition for a provisional disposition

• The documents and the stage of the proceedings: The company checks whether it has received a complaint, a petition for a provisional disposition, a court decision, or documents relating to enforcement.
• The parties and what is claimed: The company checks the name of the company named as the defendant in the lawsuit or the respondent in the provisional disposition proceedings (referred to as the obligor under Japanese law), the case number, the patent number and claims, the products, processes, and acts in question, and whether an injunction, disposal, or payment of money is sought.
• How the documents were received: The company records the sender, the date of receipt, and the department and person who received the documents, and keeps the envelopes and any electronic notices.
• Deadlines and hearing dates: The company checks the deadline for submitting a written answer or other documents and the dates of oral argument or other hearings, and assigns a person in charge.
• Technical and transaction records: The company locates specifications, drawings, physical samples, and development records for the relevant period, as well as sales and purchasing records, and preserves them so that they are not overwritten or deleted.
• Confidential information and foreign-language documents: The company identifies documents containing trade secrets or business partners' confidential information and documents in languages other than Japanese, and checks who inside and outside the company, including any overseas head office, has access to them.
• Stock, orders, and supply: The company checks its stock of the products in question, outstanding orders, scheduled shipments, and notification requirements under contracts with business partners.
• Arrangements for handling the case and approvals: The company decides its internal point of contact, the technical and accounting personnel involved, and who approves decisions. Where an overseas head office or overseas lawyers are involved, it also assigns responsibility for communication and translation.

Basic considerations in responding to an infringement allegation, such as non-infringement and invalidity, are explained in Responding to IP infringement warning letters.

1 Checking the documents, proceedings, deadlines, and arrangements for handling the case

The documents received, what is claimed, and the parties

The company sorts the documents into the complaint, the petition for a provisional disposition, any court decision, and any documents relating to enforcement. A copy of a petition for a provisional disposition may be sent directly by the petitioner.

We check the relief sought in the complaint or petition, such as an injunction, disposal of products, or payment of money. We also check which company has been named as defendant or obligor. Whether the party is an overseas head office, a company incorporated in Japan, or another group company affects both the point of contact and the materials to be prepared.

The deadline for the written answer and attendance at hearings

The company checks the deadline for the written answer and the hearing date in the complaint, the summons, and other documents. The deadline is not a fixed number of days from receipt.

If the defendant does not dispute, in a written answer or otherwise, the facts alleged by the other party and also fails to attend the first oral argument hearing, as a general rule it is deemed to have admitted those facts (constructive admission). As a result, a judgment granting the claim may be rendered. On the other hand, at the first hearing for oral argument, the court may treat the contents of a written answer or other document already submitted as having been stated (constructive statement). We consider the contents of the written answer and how to handle the hearing together.

As a general rule, the court decides a petition for a provisional disposition seeking to stop sales or similar acts after oral argument or a hearing at which the company may be present. There is an exception, however, where holding such a hearing would defeat the purpose of the petition. Hearing dates in a provisional disposition are managed separately from those in the lawsuit.

Jurisdiction and the progress of the lawsuit

Patent infringement lawsuits handled by district courts fall, at first instance, within the exclusive jurisdiction of the Tokyo District Court or the Osaka District Court, depending on the region determined under the ordinary rules of jurisdiction. This is not determined solely by the location of the defendant's head office, and where statutory requirements are met, a case may be transferred to another court.

Where an overseas company is named as defendant, the company also checks whether Japanese courts have international jurisdiction. This is because, if the defendant presents oral arguments on the merits or makes statements in preparatory proceedings without asserting that Japanese courts lack jurisdiction, Japanese courts may thereby obtain jurisdiction.

Under the hearing model published by the Tokyo District Court, the court first examines infringement and invalidity and, if it forms the view that infringement has occurred and a decision on damages is needed, proceeds to examine the amount of damages. The actual progress varies from case to case. The model also shows that settlement may be recommended once the court has disclosed its view on infringement. The court may attempt settlement at any stage of a lawsuit, and once a court settlement is entered in the electronic court record, it has the same effect as a final and binding judgment.

Managing service and arrangements in Japan and overseas

The full digitalization of civil litigation in Japan took effect on May 21, 2026. Whether the new procedures apply is checked by reference to the date on which the lawsuit was filed and similar factors. In cases governed by the new procedures, lawyers and other persons subject to the electronic filing requirement must, as a general rule, file applications and documents online. However, a complaint may still be served on paper. Service through Japan's court electronic system (electronic service) takes effect, as a general rule, at the earliest of the following: when the person to be served views the documents in the system, when that person downloads them, or when one week has elapsed from the date the notification was sent. Opening the notification email is not what determines when service takes effect. Civil provisional remedy proceedings, including provisional dispositions, are outside the scope of this full digitalization.

Service on a company located overseas is made by a method that depends on the country where service is to be made and any applicable treaty. Depending on the country and method, this may take time. Even so, from the time the company receives a copy, for example through a company incorporated in Japan, it checks whether formal service has been made and when the deadlines fall.

The company sets the lines of communication among the lawyers handling the lawsuit in Japan, the overseas head office and its local lawyers, and the persons responsible for translation. Where technical analysis is needed, we also work with patent attorneys (benrishi). A Japanese patent attorney whose registration includes the supplementary notation qualifying them to act in specified infringement litigation may act as a litigation representative in a patent infringement lawsuit if a lawyer has been retained by the same client in that lawsuit.

2 Admissions and denials, defenses, and evidence in infringement litigation

Responding to the other party's allegations and identifying the product or process

The company sorts the facts stated in the complaint, such as the structure of the product, the manufacturing process, and sales, into those it admits, those it disputes, and those it cannot determine without investigation. We match model numbers, specifications, manufacturing periods, and processes, and keep the admission or denial of facts separate from the assessment of whether they constitute infringement.

A party that denies the specific form of the product or process alleged by the other party must clarify the specific form of its own product or process, unless there is a reasonable ground for being unable to do so.

Arguments and supporting records for each issue

We divide the patent claims into their elements and compare each element with the company's product or process. Where the other party alleges, in addition to literal infringement, infringement under the doctrine of equivalents or indirect infringement (under which the supply of certain components or similar acts is deemed to be infringement), we gather records relevant to each issue in dispute. If the company asserts a right based on prior use, it gathers records showing how it completed or acquired the invention and the business using the invention, or preparations for that business, that it was carrying out in Japan at the relevant date. Explanatory materials prepared later are kept separate from contemporaneous records.

Invalidity defenses and invalidation trials

In an infringement lawsuit, the company may contest the exercise of the patent right on the ground that the patent should be invalidated (an invalidity defense). This is separate from an invalidation trial before the Japan Patent Office (JPO), in which the validity of the patent itself is contested, and requesting such a trial is not a prerequisite. Even if an invalidation trial is requested, the lawsuit proceeds unless the court decides to suspend it.

Under Japanese case law, the patent owner may counter an invalidity defense by arguing that a correction would eliminate the grounds for invalidity (a rejoinder based on correction). In that case, the company checks whether the correction would be permitted, whether it would eliminate the grounds for invalidation, and how the corrected claims relate to the product in question. If an invalidation trial is also requested, we manage the deadlines, arguments, and evidence in the lawsuit and the trial together.

Preserving and submitting evidence and preparing translations

The company preserves physical samples, drawings, specifications, source code, test results, and manufacturing records, matched to the versions used in the relevant period. When a document in a foreign language is submitted as documentary evidence, a Japanese translation of the portions the submitting party asks the court to examine must be attached.

On a party's motion, the court may order the submission of documents or electronic records necessary to prove infringement or calculate damages. We check whether submission is necessary, its scope, and whether there are justifiable grounds for refusing to submit. Japan's Patent Act also provides for a court-ordered investigation procedure in which, after an infringement lawsuit has been filed and subject to statutory requirements, a neutral expert designated by the court examines a factory or other premises. For an investigation, we consider the requirements for the order, the scope and burden of the investigation, and the protection of confidential information.

3 Responding to damages claims and managing confidential information

The basis for calculating the amount claimed and the issues in dispute

The Patent Act contains provisions on calculating and presuming the amount of damages. They include a method based on the quantity of infringing products transferred and the profit per unit of the patent holder or exclusive licensee, a method presuming the amount of damages from the infringer's profits, and a claim for an amount equivalent to a license fee, and their requirements and the circumstances that may be raised in response differ. We organize the relevant period, quantities, sales, and costs according to the calculation method used. Where the claim is based on the infringer's profits, court decisions treat the scope of costs that may be deducted from sales and whether the presumption of damages can be rebutted by performance, design, or other features other than the patented invention as separate questions.

Preserving and organizing sales and profit records

According to guidance from the intellectual property divisions of the Tokyo District Court, defendants are asked to make efforts to preserve and organize financial statements, books of account, vouchers, and similar records from the stage at which infringement is examined. The company preserves records of sales, purchases, and costs of the products in question, matched to its books and electronic data. Securing records within the company is kept separate from deciding what to submit to the court or the other party.

The scope of disclosure of trade secrets and protective procedures

Drawings, manufacturing conditions, costs, and sales by customer may include trade secrets. A confidentiality protective order is a procedure under which, subject to certain requirements, the persons to whom it is addressed are prohibited from using the trade secret concerned for purposes other than conducting the litigation and from disclosing it to persons not bound by an order covering the same secret. Third-party access to the case record, including inspection and copying, is a separate matter. A separate application is made to restrict access to the portions that meet the statutory requirements. These restrictions do not prevent the opposing party from accessing those portions.

Treating information as confidential within the company does not, on its own, necessarily establish justifiable grounds for refusing to submit it. We identify the scope of the requested submission and which parts contain confidential information, and consider protective procedures before submission.

4 Provisional dispositions and business continuity

The petition stage and after an order is issued

Receiving a petition for a provisional disposition does not mean that an injunction has been ordered. In a provisional disposition seeking to stop sales or similar acts, the petitioner must make a prima facie showing, with supporting materials, of both the right to seek an injunction based on the patent right (the right to be preserved) and the need for an injunction without waiting for a judgment in order to avoid substantial harm or imminent danger (the necessity of preservation). The company prepares its arguments and supporting materials separately for these two points.

If an injunction order is issued, the company checks the products covered, the prohibited acts, and the companies bound, by reference to the operative part of the order and its attachments, and also checks the status of service and enforcement. Under Japan's provisional remedy procedure, the company may file an objection with the court that issued the provisional disposition order. Filing the objection does not automatically stay enforcement. A stay of enforcement requires a separate application and an order from the court finding that the statutory requirements are met. Security, the handling of hearings, stays of enforcement, and revocation procedures are explained in detail in Responding to a provisional disposition (interim injunction) to stop pharmaceutical sales immediately before launch.

Stock, orders, and continuing or changing manufacture and sales

Even before any injunction order is issued, a product that infringes a patent may be subject to an injunction or a damages claim. The company considers whether to continue manufacture and sales, to stop them, or to change the design, taking into account the outlook on infringement, stock and orders, and the effect on supply to business partners.

For a redesigned product, whether it infringes is considered afresh. Changing the design also does not automatically extinguish any liability that arose from acts before the change. The company also preserves physical samples and records of the product before the change.

Settlement terms and explanations to business partners

In both a lawsuit and a provisional disposition, settlement may be considered alongside the defense. We organize the patents and products concerned, payments for past acts, terms governing future practice of the patented invention, and the handling of stock, and check the scope of the company's internal approvals.

Explanations to business partners are given according to the stage of the proceedings and the products concerned. The company also checks notification and indemnity clauses in supply contracts.

Frequently asked questions

How we assist with patent infringement litigation and provisional dispositions

We offer consultations on individual matters involving representation in patent infringement lawsuits and provisional dispositions, preparing written answers and briefs, organizing technical records and evidence, assessing invalidity defenses and invalidation trials, damages records and the protection of confidential information, procedures after a provisional disposition injunction order, and settlement negotiations and explanations to business partners.

Making an inquiry

Please tell us, as far as you know, the type of documents received and the date of receipt, the hearing dates and deadlines stated, the patents and products concerned, and your communications with the other party so far.

Key legislation and official sources

English translations of legislation are provided for reference and may not reflect all amendments in force. The Japanese texts are authoritative. English descriptions of Japanese-only sources are supplied for reference and are not official English titles.

Article topic	Legislation or official source	Source type
Written answer, constructive statements, constructive admission, jurisdiction, transfer, settlement, service abroad, electronic service and electronic filing	Code of Civil Procedure (民事訴訟法)	Japanese text: e-Gov Law Search (current version, reflecting amendments in force as of June 24, 2026). English translation: Japanese Law Translation, for reference
Content of the written answer, service of the complaint, translations of foreign-language documentary evidence	Rules of Civil Procedure (民事訴訟規則)	Japanese text published by the Supreme Court of Japan (courts.go.jp)
Specific form of the product or process, prior use, invalidity defense, suspension, submission of documents, investigation, damages, confidentiality protective orders	Patent Act (特許法)	Japanese text: e-Gov Law Search (current version, reflecting amendments in force as of June 24, 2026). English translation: Japanese Law Translation, for reference
Requirements for provisional dispositions, objection, stay of enforcement	Civil Provisional Remedies Act (民事保全法) and Rules of Civil Provisional Remedies (民事保全規則)	Act: e-Gov Law Search. Rules: Japanese text published by the Supreme Court of Japan
Patent attorneys as litigation representatives	Patent Attorney Act (弁理士法)	Japanese text: e-Gov Law Search
Full digitalization of civil litigation and electronic service	Courts in Japan, 「改正民事訴訟法・改正民事訴訟規則の概要」 (Overview of the amended Code of Civil Procedure and Rules of Civil Procedure)	Official procedural information in Japanese
Hearing model and preparation for the damages phase	Tokyo District Court, Intellectual Property Divisions: guidance on the hearing model for patent infringement litigation and on hearings concerning damages	Official court guidance in Japanese
Confidentiality protective orders and restrictions on access to the case record	Tokyo District Court, Intellectual Property Divisions: guidance on confidentiality protective orders and on applications to restrict access to the case record	Official court guidance in Japanese
Service abroad	Hague Conference on Private International Law (HCCH): Service Convention, Central Authority and practical information pages for each state	Official information in English

Legal information reviewed: October 11, 2026

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This article is provided for general informational purposes only and does not constitute legal advice on any specific matter. Please consult us regarding your specific situation. The content is based on the laws and regulations in effect as of the date of the last update.