A US utility patent lasts 20 years from the earliest non-provisional filing date — that's the rule that controls everything else. It's not 20 years from the issue date, not 17 years (the pre-1995 rule), and not "until you stop paying."
The actual expiration date for a specific patent is filing date + 20 years, modified by:
- The maintenance fee schedule (miss one and the patent dies early)
- Patent Term Adjustment (PTA) — extra time the USPTO owes you for prosecution delays
- Patent Term Extension (PTE) — extra time for FDA-regulated products
- Terminal disclaimers that align expiration with a related earlier patent
For a defendant, the expiration date is one of the first numbers to look up. An expired patent can't be infringed forward, and damages for past infringement are bounded by a six-year limitations period under § 286.
The 20-year rule
The clock starts at the earliest non-provisional filing date (or the earliest application from which priority is claimed if it's a continuation/divisional). It does not start at:
- The provisional filing date (provisionals don't anchor the term)
- The issue date (irrelevant for term)
- The priority date in a foreign filing (controls novelty, not term)
This trips up a lot of people. A patent that issued in 2020 from a 2002 application expires in 2022, not 2040.
The rule was set by the Uruguay Round Agreements Act (URAA) in 1995. Patents filed before June 8, 1995 may instead get the greater of 17 years from issue or 20 years from filing — relevant only for very old patents still in litigation today.
Maintenance fees
Three maintenance fees keep the patent alive past issue:
- 3.5 years after issue
- 7.5 years after issue
- 11.5 years after issue
Miss one and the patent expires early. The USPTO does not chase you. There's a 6-month grace period (with a surcharge) after each due date; after that the patent goes abandoned for failure to pay maintenance.
This is why so many older patents are quietly dead. About half of issued US patents go abandoned at the 11.5-year fee — owners decide the patent isn't worth the four-figure renewal. A defendant should always check fee status on USPTO Patent Center; an asserted patent that's actually expired is a fast win.
Patent Term Adjustment (PTA)
The USPTO is supposed to act on applications within set deadlines. When it doesn't — when the examiner takes too long to issue an office action, or the PTO sits on an application — the applicant can claim PTA: extra days added to the 20-year term to compensate.
PTA is calculated by the USPTO and printed on the patent's first page (the "(*)") notice. PTA can add anywhere from a few days to several years; for slow-prosecuted technologies (biotech, complex chemistry) it routinely runs 1–3 years.
Applicants can also lose PTA through their own delays — failing to respond to office actions on time, filing supplemental papers, etc. Net PTA is the USPTO delays minus the applicant delays.
Patent Term Extension (PTE)
Drugs, medical devices, and color additives that need FDA approval can claim PTE under 35 U.S.C. § 156: up to 5 years to compensate for time lost to FDA review. Maxes the total term at 14 years from FDA approval. PTE is granted for one patent per regulatory product.
PTE is heavily used in pharma. A patent on a small-molecule drug that took 8 years through FDA can recover up to 5 of those years on the back end, pushing effective term well past the nominal 20.
Family priority and terminal disclaimers
Continuations and divisionals filed during prosecution claim priority back to the original parent. The 20-year term runs from the parent's filing date — so a continuation that issues in 2020 from a 2005 parent expires in 2025, not 2040.
Terminal disclaimers are sometimes filed during prosecution to overcome obviousness-type double patenting rejections. A terminal disclaimer ties the expiration of one patent to the expiration of an earlier patent in the same family. Net effect: the disclaiming patent expires when the earlier one does, regardless of its own filing or PTA.
What expiration means for defendants
A few practical consequences:
- Expired patents can't be infringed going forward. Once the patent expires, the technology is in the public domain and anyone can practice it freely.
- Damages on past infringement are capped at 6 years. § 286 sets the limitations period — even if a patent was infringed for 15 years before it expired, the patentee can only recover damages for the 6 years before suit.
- Re-examination and IPR can still target an expired patent, though the use case is narrow (cleanup of related family members, mostly).
- A patent in its last 18 months is a settlement-leverage problem for the troll, not the defendant. The closer to expiration, the smaller the maximum monetizable window — and the smaller the rational settlement demand.
For patents in our database, the Extensions section of each dossier covers PTA, PTE, family expiration, and the projected end-of-term date.
Bottom line
A patent's term is 20 years from the earliest non-provisional filing, modified by maintenance fees (which kill many patents early), PTA (which extends), PTE (which extends in pharma), and terminal disclaimers (which can shorten). Look up the actual expiration before doing anything else — about half of all granted patents are abandoned by year 11.5, and an expired patent is the easiest defense in the world.
Related: What is a patent?, How to obtain a patent.
This article is for general education and is not legal advice.