The Doctrine of Equivalents: Why Your Amazon Patent Complaint Is More Complicated Than It Looks

The part of patent law most sellers have never heard of — and why it might be the most important part of your case.

Disclaimer: Prior results do not guarantee a similar outcome.

When a patent complaint hits your Amazon account, there is a very natural thing to do: pull up the patent, look at the claims, compare your product, and see how different they are.

If they look different enough, you feel okay. You move on.

This is one of the most costly mistakes in Amazon IP law.

Patent protection does not end at the literal language of the patent’s claims. There is a legal doctrine — the doctrine of equivalents — that extends a patent’s reach beyond its exact words. Under this doctrine, a court can find infringement even when a product does not match the patent claim for claim. The test is whether the accused product performs substantially the same function, in substantially the same way, to achieve substantially the same result. If the answer is yes across all three, infringement can be found — regardless of how different the products look on the surface.

Our litigation and arbitration team is working on a case right now where this is the central issue. The client’s product is not a copy of the patented design — that is not in dispute. What is in dispute is whether the materials and construction are close enough, under the doctrine, to fall within the patent’s scope. That is an entirely different and significantly more complicated question than whether it looks the same.

To answer it, our senior attorney Brian Malkin reached out to the client’s manufacturer overseas and obtained a formal declaration describing the specific material properties of the product. Not a general letter. A detailed technical document that addresses, in precise terms, the question the legal standard actually asks. That declaration forms the backbone of the defense — it establishes that the product’s materials differ from the patented invention in ways that hold up legally, not just visually.

This is what patent defense actually looks like. It is not a response to Amazon explaining that your product is different. It is a layered analysis of specific claim limitations, backed by documentation from the people who built the product, submitted through the proper channels.

A patent is a legal monopoly — the exclusive right to make, use, and sell a specific invention. When a patent holder believes a seller is infringing it, the burden falls on that seller to demonstrate they are not. Meeting that burden requires more than a surface comparison. It requires understanding what the patent covers in its fullest legal scope and building a defense that meets that scope directly.

If you have received a patent infringement complaint on Amazon, you have not automatically lost. But every day that passes without the right legal analysis in place is a day your listing is more vulnerable — and a day your options for a clean resolution get narrower.

Do not respond to anything until you have spoken with our team.

Contact Rosenbaum & Segall before you file anything. Visit amazonsellerslawyer.com or call 212–256–1109.