What is a terminal disclaimer? You have filed multiple patent applications, and your examiner is now asking for one. What does this mean?
One nice feature of the US patent system is that it allows you to develop your ideas over time by filing different but related patents. So long as you follow the rules, you can build on your initial ideas without the USPTO using your original work against you.
However, the idea of a patent is that in exchange for disclosing some invention of value, society may grant you a limited monopoly for a limited period of time. This is usually no more than about 20 years. So, what prevents an inventor from trying to extend the lifetime of their patent forever by continuing to file minor variations?
Impact on your patent’s lifetime
This is why the USPTO requires terminal disclaimers. (See the rules). If you do it right, the USPTO will let you file additional patent applications. But the terminal disclaimer requirement means that these later applications won’t last longer than the first. Say you filed your first invention in 2020, and it will expire 20 years later in 2040. Then you file a related application ten years after the first. Because of the terminal disclaimer requirement, it will expire in 2040 rather than 2050.
The examiner will usually offer the terminal disclaimer on a “take it or leave it” basis. That is, if you don’t take it, then you won’t get the patent! However, sometimes there is room for negotiation. Do some of the newer claims overlap with the earlier claims, but some do not? See if you can negotiate. Perhaps you can tweak the claims and avoid the terminal disclaimer.
When are terminal disclaimers used?
Here are two examples where these may come up:
First patent: claim 1. A widget comprising [widget description]; wherein said widget has blinking lights.
You later realize that the blinking lights are not needed. So you file a continuation patent that makes original claim 1 broader by removing the requirement for the blinking lights.
Second patent: claim 1. A widget comprising [widget description].
Suppose the examiner thinks that “claim 1 [widget description]” also deserves a patent. In that case, the examiner will require one or more terminal disclaimers so that your second patent will expire at the same time as the first patent.
First patent: claim 1. A widget comprising [widget description].
Later, but before the first patent was issued, you realized that the device could be much cooler. You think of a smartphone app to remotely control it. Now you want to add a smartphone app to your second patent discussion and put this in the claims.
Second patent: claim 1. A smartphone-app-controlled widget comprising [widget description]; wherein said widget is configured to be remotely controlled by a smartphone app running on a smartphone.
The USPTO may let you do this. But again, the price for letting you add smartphone app control is also one or more terminal disclaimers. Either way, regardless of removing or adding stuff, you can’t extend the lifetime of your original patent.
When the patent issues, the front page will issue with the filing date, and a small asterisk “*” after it. This refers to: “* this patent is subject to a terminal disclaimer.” In addition to the document itself, the USPTO will also require a terminal disclaimer fee, presently $170. You can see an example of a terminal disclaimer form here.