In principle, a patent lasts a maximum of 20 years. In practice, it can run to 21 years or more. Why? Because patents, like everything else, come with exceptions to the rule.
Fortunately, you don't need to worry about most of them. We'll handle that. But the life of a patent is worth watching yourself, especially if you're using a patent database to check whether a competitor's patent has expired. We've seen this go badly wrong in practice.
So does a patent expire after 20 years? Here are three exceptions.
1. The priority year
When you file a patent application, that filing date becomes your priority date. The 12 months that follow are the priority year.
Use that year well and you push your patent's expiry date back by a year. Counting from your first filing, your protection runs for 21 years instead of 20. It's a useful trick, and your patent attorney can help you make the most of it.
2. Not every country is the same
The standard 20-year term applies in most countries, but not all.
Brazil is one exception. There, a patent runs for 10 years from the date it's granted. Since granting can take 12 years or more, assuming a 20-year maximum could lead you badly astray.
The United States had a similar system until 8 June 1995, with patents running up to 17 years from grant. US patents filed before that date can therefore still be in force.
Some countries, including the US and South Korea, also grant extra protection if the granting process took a long time. Those rules vary too.
3. Medicinal products are an exception
Medicines can get longer protection through a Supplementary Protection Certificate (SPC), which extends a patent by up to five years.
Before a medicine reaches the market, years of research go into proving it's safe. The European Medicines Agency only issues a marketing authorisation once a medicine is shown to be safe and effective.
An SPC compensates for that lost time, giving the patent holder five more years to earn back the investment.
