When do patents expire?
A patent expires when its legal protection ends, either because its maximum term has run out or because a required patent renewal fee was not paid. Once it expires, the owner can no longer stop others from making, using or selling the invention.
What is the normal term?
In most countries, 20 years from the filing date. The clock starts at filing, not at grant, which means the years spent waiting for the patent office to examine the application come out of the term.
For example a patent granted after four years of examination therefore has about 16 years of enforceable life left, not 20.
What makes a patent expire early?
Two things.
- An unpaid patent renewal fee. The most common cause, and the only avoidable one.
- Voluntary abandonment. The owner decides the patent is no longer worth maintaining and stops paying.
Both end protection in that country only. A patent lapsing in Germany has no effect on the same invention's patent in Japan.
Can an expired patent be brought back?
If it reached the end of its term, no. That date is final.
If it lapsed for non-payment, sometimes. Most jurisdictions allow a grace period with a surcharge, and some allow restoration after that, though it is discretionary and time limited. See what is an expired patent for how expired, lapsed and abandoned differ.
What happens to the invention afterwards?
It enters the public domain. Anyone can make, use or sell it freely, and no permission or licence is required.
