A patent is only useful if you can enforce it. Enforcing a patent means hiring a lawyer, going to Federal court, and filing a lawsuit. Or at least threatening to do so. But how real is your threat?
Federal law allows you, the patent owner, to collect money damages for patent infringement that occurs after you file suitand for six years prior to the date that you file suit. That’s a pretty big threat.
There’s a limit. You can only collect past money damages if the infringer is on notice that your product is patented. But how does the infringer learn about your product and your patent?
Two ways. The first is by actual notice, from you to the infringer (“Dear Infringer…”). The second is “constructive notice” by “patent marking,” which is when you mark your product with ‘patent’ or ‘pat.’ followed by the patent number. Alternatively, you can mark your product with ‘patent’ or ‘pat.’ and an address of a website with patent information on the product. If your product is too small or delicate to be marked (for example, a pill or a liquid), you can mark the packaging.
Does the infringer actually have to know about your product or your patent to be subject to six years of infringement damages? Absolutely not. ‘Constructive notice’ by patent marking is enough.
So patent marking is very, very important to actually enforcing your patent. What about when you license your patent to someone else, who produces and sells the product?
This was the situation presented by VDPP v Volkswagen, decided August 19, 2026. VDPP licensed its patent to eleven different entities, which manufactured and sold the patented product but did not include patent markings on the products. Volkswagen allegedly infringed the patent. In the interim, the patent expired, and VDPP sued Volkswagen for patent infringement. Since the patent had expired, there was no ongoing infringement and no ongoing patent damages. The only possible damages were for past infringement during the six years prior to filing the lawsuit.
Both the lower court and the Federal Circuit dismissed the case, holding that VDPP failed to allege that Volkswagen had actual or constructive notice of the patent because VDPP’s licensees failed to include patent markings on the products. The trial court also awarded Volkswagen attorney’s fees of $200,000 as a sanction against both VDPP and its attorney for bad conduct and for bringing a case with no merit.
The bottom line? Include a patent marking on your patented product. If you license your patent to others, your license agreement had better specify that the licensee (the person who licensed the patent from you) mark the product as patented with the patent number, and you had better ensure that the licensees do so. And don’t be “frivolous and objectively unreasonable.”
— Robert Yarbrough, Esq.