A patent notice letter is usually a pre-suit allegation, not a judgment. The sender claims you make, use, sell, offer, or import something that practices one or more claims. Treat the letter as a risk event: it can start a willfulness and damages-notice story, and it can be the last quiet window before a complaint, an ITC section 337 filing, or both.
Should I ignore a patent notice letter?
Usually no. Ignoring a clear allegation can leave you less prepared if a suit follows. Under 35 U.S.C. 284, a court may increase damages up to three times the amount found or assessed. After Halo Electronics, Inc. v. Pulse Electronics, Inc., 579 U.S. 93 (2016), that enhancement path turns on culpable, often egregious infringement conduct measured at the time of the conduct, not on every garden-variety infringement finding. Pre-suit notice is frequently how plaintiffs later allege that you knew and kept going. That does not make trebling automatic, and it does not mean every letter is a lawsuit tomorrow. It means the letter belongs on a calendar with a file.
What should I do in the first 48 hours?
Save the envelope, email headers, attachments, and any prior correspondence. Put a short litigation-style hold in place so people stop deleting product files, source code, sales data, and chat threads that touch the accused products. Calendar any reply deadline the letter states, plus a near-term internal deadline to finish a triage memo. Identify the patent numbers, the claims if listed, and every product, SKU, or service the letter names. Do not call the sender's lawyer for an informal product tour without your own counsel on the line.
What facts should counsel help me gather?
Build a one-page map: patents and claims cited, accused products and versions, when you first sold or imported those products, who manufactures or supplies key parts, and whether customers or distributors already received a copy. Pull the patents from the USPTO, skim the claims, and collect design documents, datasheets, and prior art you already know about. Check insurance notice requirements and any indemnity clauses with suppliers or OEMs. Separately ask whether the letter is trying to create actual notice for damages under 35 U.S.C. 287(a); marking and willfulness are related notice themes but different doctrines.
Do I need an opinion of counsel right away?
Not always on day one, but many companies ask counsel early whether a written non-infringement, invalidity, or unenforceability opinion is worth the cost on these patents. An opinion is not a complete shield under Halo, and a rushed memo that ignores the claims can hurt more than it helps. Counsel can also help you decide whether a short acknowledgment, a detailed reply, or silence for a short window fits the letter's tone and your commercial risk.
What reply strategies are common?
Common paths include asking for claim charts or more detail, explaining a non-infringement position, pointing to prior-art themes at a high level, proposing a license discussion, or saying you need time to investigate. Avoid inventing technical admissions in an email to the other side. Avoid promising a redesign date you cannot meet. If the letter is vague, saying you cannot evaluate the allegation without claim-by-claim detail is often reasonable. If the letter cites only a provisional application, see the provisional cease-and-desist FAQ; a provisional is not an issued patent.
What risks grow if I sit on the letter?
The owner may file a district-court complaint under 35 U.S.C. 281, seek a faster import remedy at the ITC under 19 U.S.C. 1337, or both. Pre-suit notice can support a willfulness plea and a request for enhanced damages under section 284 if a case later goes that far. Related reading: the willfulness breakout, the dual-track ITC page for owner-side import pressure, and the patent-marking breakout for the section 287 damages window.
What defensive tools should I put on the table?
Accused companies often evaluate design-arounds, license talks, a declaratory judgment action in an appropriate court, ex parte reexamination, and AIA trials at the PTAB such as IPR or PGR when the timing and prior-art record fit. PTAB and reexamination are tools the accused side can initiate; an ITC complaint is a parallel pressure track the patent owner can open. Fintiv and related discretionary-denial practice can affect whether an IPR is instituted when a district case is already moving, so timing matters. If papers arrive, the one-year IPR clock after service of a complaint under 35 U.S.C. 315(b) becomes part of the calendar.
When should I escalate beyond a quiet investigation?
Escalate when the letter names customers, threatens suit on a short clock, attaches claim charts, coincides with a competitor launch, or lands while you are raising money, selling the company, or shipping a new SKU. Also escalate if you learn of a related ITC complaint receipt or a suit against a peer on the same patents. Watch for follow-up letters, service of a complaint, or customer demands for indemnity.
Where should I read next on this site?
If a complaint arrives, read the longer sued FAQ for the deep checklist and the district-court next-steps FAQ for the short sequence after service. For PTAB timing, read the PTAB challenge FAQ and the Fintiv breakout. For willfulness risk after notice, read the willfulness breakout. For customer letters about your product, read the indemnity and customer FAQ. For ITC naming, read the ITC complaint FAQ and the dual-track breakout. For provisional-only letters, read the provisional cease-and-desist FAQ.