A competitor filed a possible blocking patent in your field. Now what?

You found a competitor's filing in your CPC subclass and it looks uncomfortably close to your product. First, slow down: most of the blocking patent risk depends on three facts you can check yourself in an afternoon, for free. Is it an application or a granted patent? What do its claims actually cover? Where is it in examination? Then decide, with a patent attorney, whether to design around it, challenge it, license it or simply keep watching.

Start with the kind code printed after the document number. On USPTO documents, A1 is a patent application publication, and A2 and A9 are republished or corrected publications. B1 is a granted patent that had no earlier published application, and B2 is a granted patent that did.

The difference matters. Infringement under 35 U.S.C. 271(a) is making, using, offering to sell or selling a patented invention in the United States, or importing it, without authority. A published application is not yet a patent. It may be granted as filed, granted with narrower claims, or not granted at all.

It is not harmless either. Under 35 U.S.C. 154(d), a granted patent can include a right to a reasonable royalty from anyone who used the invention between publication and grant, if that person had actual notice of the published application and the issued claims are substantially identical to the published ones. Treat a close application as something to plan around, not something to ignore.

Also check the basics: is the document a US filing (US patents are enforced in the United States), and does the assignee match the competitor you think it does?

The title, abstract and drawings describe the invention broadly. The legal scope is in the claims, the numbered paragraphs at the end that, under 35 U.S.C. 112(b), must particularly point out and distinctly claim the subject matter. Read them like this:

1. Find the independent claims. They do not refer to another claim ("1. A device comprising..."). Dependent claims ("2. The device of claim 1, wherein...") add features and are narrower.
2. Split each independent claim into elements. Each feature after "comprising" is one element. Put them in rows.
3. Compare element by element with your product. For each element, write "yes", "no" or "unsure", with the part of your design it maps to.
4. Note what is missing. If your product clearly lacks an element of a claim, write down which one and why. That note is useful to your attorney, but whether it actually avoids the claim is a legal question.

A filing can change a lot after you first see it, so check where it stands.

• Status and documents. The USPTO points to Patent Center for application status and to the Open Data Portal's Patent File Wrapper for file documents. Patent Center no longer allows guest access, so you need a registered account. Look for rejections, amendments to the claims and a notice of allowance.
• Family. A later application can claim the filing date of an earlier pending one under 35 U.S.C. 120. So one publication can lead to several related applications with different claims. Ask your attorney to check the whole family, not just one document.
• Term. A US utility patent term generally ends 20 years from its US filing date (35 U.S.C. 154(a)(2)). A granted patent also expires early if a maintenance fee is not paid at 3.5, 7.5 or 11.5 years after grant, within a six-month grace period (35 U.S.C. 41(b)). An old patent may be close to expiry.

Write each check and its date in your log. Status changes are the moments when your options open or close.

Third parties have a few formal routes at the USPTO. Each has strict rules, and most are best handled by a practitioner.

Some details of the preissuance route catch people out. The deadlines cannot be waived, and a submission on the deadline day itself is late. The submitter does not have to name a real party in interest but cannot be anonymous. The submission is filed through a web interface in Patent Center, and a non-compliant one is discarded. A fee applies per ten items, but none is due for a first submission of three or fewer items made with the required statement. After filing, a third party may not contact the examiner.

If you know of older public material (your own earlier product literature, a conference paper, an expired patent) that shows the same idea, write it down with its date. It may matter for any of these routes.

What you are really asking is whether you are free to make and sell your product. Patent professionals call this a freedom-to-operate (FTO) determination. WIPO recommends doing a preliminary FTO review early in product development, repeating it at each stage because new applications keep being filed and granted, and having qualified professionals carry out the more extensive search and legal analysis before committing to a design.

Call a patent attorney now if any of these is true:

• An independent claim seems to cover something you make, sell or are about to launch.
• The filing is a granted patent, or you see a notice of allowance.
• You are considering a redesign, a license, a challenge or a preissuance submission.
• The competitor has contacted you about the filing.

To find one, use the USPTO's register of active patent practitioners. The USPTO cannot recommend a specific attorney or agent; for lower-cost help it points to law school clinic and patent pro bono programs. Bring your log, the claim chart from step 2 and your status notes. A focused question ("do claims 1 and 12 cover our design?") gives your attorney a clear starting point.

Whatever you decide, write it down: the date you first saw the filing, the claims you compared, each status check, who reviewed it and what was agreed. If a redesign was considered, note what changed and why. A clean record helps your attorney and makes the next review faster.

Then go back to your weekly watch. A close filing may have related applications in the same family (see step 3). If you do not have a routine yet, the guide on tracking competitor patent filings with a free manual watch shows how to set one up with free USPTO tools.