Can an expired patent still be prior art against a pending application?

Yes, an expired patent is still prior art. Prior art has nothing to do with whether a prior patent is live or dead. The relevance and content of the teaching are what matters. Therefore, an expired patent is no different from, for example, a white paper in that both contain publicly accessible information that could block a later-filed patent application claiming the same invention or concepts.

In the same way, a published patent application can also serve as prior art even if the application never matured into an issued patent.

What is an expired patent?

An expired patent means that it is no longer enforceable. So there is no risk of an infringing a dead patent. The owner cannot use a dead patent to stop others from copying or otherwise using the technology claimed in the patent.

However, the expiration of a patent does not stop the document from being used to block future patent applications for similar inventions.

How can you check if a patent has expired?

Unlike design patents, utility patents need to be “renewed” periodically by maintenance fees. You can check on the status of a particular patent’s maintenance fee here.

Can you patent something similar to a dead patent?

If you’re thinking of applying for a patent on an invention similar to what is shown in an old patent, your invention must still be novel and nonobvious. You cannot re-patent a previously patented invention.

Need help with filing a patent application?

Are you thinking about filing a patent application, but you’re not sure if you should move forward? Call (949) 223-9623 or email to explore whether it would make sense to apply for a patent.

The following two tabs change content below.

Vic Lin

Startup Patent Attorney, Cofounder at Innovation Capital Law Group
We align ourselves with Davids fighting Goliaths. We have helped clients obtain 700+ granted patents, 500+ registered trademarks and countless foreign IP registrations. Let's get to work on your IP: (949) 223-9623 |

Latest posts by Vic Lin (see all)