A patent warning letter can open negotiations about suspected infringement in China, but it can also prompt the recipient or an interested party to seek a court declaration of non-infringement. Before sending one, verify the Chinese patent, preserve evidence, define the accusation and prepare for a response requiring you to withdraw the warning or bring proceedings. A letter does not establish infringement or compel the recipient to stop.
This guide is for overseas businesses and their counsel assessing a warning based on a granted Chinese patent. Official sources were checked on October 29, 2026. The preparation steps below are editorial recommendations, not a statutory letter template or advice on a particular dispute.
Check the right and the sender's authority
Build a short rights file containing the Chinese patent number, patent type, current owner, granted text and current legal status. Check recorded transfers, relevant licenses and authority to act for the owner. Do not substitute a U.S. patent number or an ungranted application for the Chinese patent being asserted.
Under Article 64 of China's Patent Law, invention and utility-model protection is determined by the claims, with the description and drawings available for interpretation. Design protection is determined by the design shown in the drawings or photographs, with the brief explanation available for interpretation. A product photograph that looks similar is not a complete infringement analysis.
For a utility model or design, discuss the available patent evaluation report and its findings with counsel. It is evidence, not an infringement judgment or a guarantee of validity. Our patent evaluation report guide explains that separate preparation task.
Preserve what may change after delivery
Before alerting the other side, consider whether listings, samples or transaction records may disappear. Preserve lawfully obtained originals, capture dates, seller details, URLs, purchase records and the connection between the tested item and the accused business. Keep working annotations separate from original files.
Create a comparison that identifies the specific product model or process, the relevant patent claims or design views, the evidence supporting each point and facts still unknown. Do not fill technical gaps with assumptions. Ask counsel whether additional evidence preservation is needed before the letter is sent.
Keep the accusation and recipient list precise
As a drafting recommendation, identify the sender's capacity, Chinese patent, accused conduct, product or process, factual basis, requested action and a response contact. Separate proven facts from matters needing explanation. Have counsel assess any proposed deadline and settlement request; a deadline chosen in your letter is not automatically a legal deadline.
Review every proposed recipient, including customers, distributors and investors. In a Supreme People's Court ruling dated August 2, 2024 and published April 8, 2026, a broadly worded patent allegation sent to an investor supported a non-infringement dispute by affected companies. The court explained that an unclear patent or product reference does not necessarily prevent it from defining the dispute using the warning's impact, claims and evidence. This was a jurisdiction ruling, not a final decision that the products infringed or did not infringe.
The practical lesson is to check accuracy and audience before sending. Deliberately vague allegations do not reliably avoid litigation risk.
Understand the written-demand trigger
Article 18 of the Supreme People's Court's patent infringement interpretation, effective January 1, 2010, addresses a particular sequence:
A rights holder issues a patent infringement warning.
The warned person or an interested party sends a written demand that the rights holder exercise its right to sue.
The rights holder neither withdraws the warning nor files suit within one month after receiving that written demand, or within two months after the written demand was sent.
The warned person or interested party brings a suit seeking confirmation that its conduct does not infringe the patent; the provision directs the court to accept it when the conditions are met, subject to applicable procedural requirements.
These periods run from the later written demand and its receipt or dispatch, not simply from your original warning letter. They are months, not a shorthand for 30 or 60 days. This is a patent-specific provision; this guide does not apply those periods to trademark or copyright warnings.
Assign someone to handle the reply
Before dispatch, nominate a person to receive correspondence, preserve delivery evidence and alert Chinese counsel promptly. Log the demand's dispatch date, actual receipt date, sender, affected products and requested action. Counsel should assess the trigger and calculate the applicable periods from the actual record.
Do not assume ongoing commercial discussions pause the Article 18 process. A negotiation plan should include a decision point for withdrawal, litigation or another legally assessed response. Withdrawal should also be reviewed for its scope, recipients and evidence; it is not a guarantee that every related dispute disappears.
Choose the sequence around the business objective
Decide whether the immediate objective is preserving evidence, stopping a specific activity or negotiating a license. Article 65 of the Patent Law provides for negotiation and, where parties are unwilling to negotiate or negotiations fail, litigation or a request to the patent administration department. It does not make a warning letter an automatic prerequisite to every patent action.
A private letter also does not replace the separate requirements of a platform complaint, administrative proceeding or court preservation application. Review the appropriate sequence through our China IP enforcement service. Overseas law firms can use our foreign associate coordination page to organize a China-side handoff.
For an initial inquiry, share the public patent number, the parties' names for a conflict check, public product links, the intended result, timing and budget. Complete conflict and confidentiality arrangements before supplying sensitive files or unpublished technical details. General screening is not a formal legal opinion.