A US patent expires 20 years after its US filing date if it is a utility or plant patent, and 15 years after its grant date if it is a design patent. Those baseline dates can move: missed maintenance fees can end a utility patent early, USPTO processing delays and FDA review time can push expiration later, and a terminal disclaimer can tie one patent’s death to another’s. Getting the exact date right means starting from the right anchor and then layering on whatever applies.
The Baseline Term for Each Patent Type
Federal law sets three separate clocks depending on what the patent protects.
Utility patents cover new and useful processes, machines, manufactured items, and chemical compositions. They expire 20 years from the date the non-provisional application was filed in the United States. If the application claims priority to an earlier US non-provisional through a continuation or divisional filing, the 20-year clock runs from that earliest US filing date instead.1Office of the Law Revision Counsel. 35 USC 154 – Contents and Term of Patent
Plant patents, which protect new plant varieties reproduced asexually, follow the same 20-year-from-filing rule.1Office of the Law Revision Counsel. 35 USC 154 – Contents and Term of Patent
Design patents protect the ornamental appearance of an item rather than how it functions. They expire 15 years from the date the patent is granted, not the date it was filed.2Office of the Law Revision Counsel. 35 USC 173 – Term of Design Patent
Two anchor-date questions come up often. Foreign priority claims under filing treaties do not shorten a utility or plant patent’s term; the 20-year countdown uses only the US filing date or the earliest US continuation filing date.1Office of the Law Revision Counsel. 35 USC 154 – Contents and Term of Patent Provisional applications sit outside the calculation entirely, so a non-provisional filed a year after a provisional starts the 20-year term on the non-provisional’s filing date.
Patents that issued from a PCT international application work differently. The 20-year term runs from the international application’s filing date, not from the date the applicant entered the US national stage.1Office of the Law Revision Counsel. 35 USC 154 – Contents and Term of Patent
One older-patent boundary is worth flagging. The 20-year-from-filing rule arrived through the Uruguay Round Agreements Act. Patents already in force on June 8, 1995, or those from applications filed before that date, get whichever term is longer: 20 years from filing or 17 years from grant.3United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2701 Some patents from that era ran past their 20-year-from-filing date for that reason.
Maintenance Fees Can End a Utility Patent Early
A utility patent does not automatically survive its full 20 years. The owner must pay maintenance fees to the USPTO at three points after grant, or the patent lapses. Payments are due at 3.5 years, 7.5 years, and 11.5 years after issuance.4United States Patent and Trademark Office. Maintain Your Patent Each window opens six months before the due date, and a six-month grace period follows the deadline with a surcharge. Miss the grace period, and the patent expires no matter how many years remained on the base term.
Design patents and plant patents carry no maintenance fees. They run the full statutory term without any further payments to the USPTO.4United States Patent and Trademark Office. Maintain Your Patent
What Can Push the Expiration Date Later
Two statutory mechanisms add days to a patent’s life. They address different problems.
Patent Term Adjustment for USPTO Delays
Patent Term Adjustment compensates for delays the USPTO causes during examination. The statute adds one day of patent life for each day the office falls behind certain benchmarks: failing to issue a first response within 14 months of filing, taking more than four months to respond to an applicant’s reply, or failing to grant the patent within three years of filing.5Office of the Law Revision Counsel. 35 US Code 154 – Contents and Term of Patent, Provisional Rights Delays caused by the applicant, like time extensions, are subtracted from the adjustment. The net PTA days appear on the front page of the issued patent.
Patent Term Extension for Regulatory Review
Patent Term Extension applies to a narrower set of products: drugs, medical devices, food additives, and certain veterinary and agricultural chemicals that need government approval before sale. When regulatory review consumes years of the patent term before the product can reach the market, PTE restores some of that lost time.6United States Patent and Trademark Office. Patent Term Extension Under 35 USC 156 The extension is capped at five years, and the total remaining patent life after extension cannot exceed 14 years from FDA approval.7Office of the Law Revision Counsel. 35 USC 156 – Extension of Patent Term Only one patent per approved product qualifies, and the request must be filed before the original term expires.
FDA Exclusivity Is a Separate Clock
PTE is often confused with FDA regulatory exclusivity, but they are different protections. Regulatory exclusivity blocks the FDA from approving competing generic or biosimilar products for a set period regardless of patent status: new chemical entities get five years, orphan drugs get seven, and certain pediatric studies add six months on top.8Food and Drug Administration. Frequently Asked Questions on Patents and Exclusivity Exclusivity can outlast a patent or fall short of it, so the patent expiration date alone does not tell you when generic competition can begin.
Terminal Disclaimers Can Pull the Date Earlier
When an inventor files multiple applications on closely related inventions, the USPTO may reject the later one for double patenting. The standard cure is a terminal disclaimer: the applicant voluntarily shortens the later patent so it expires on the same day as the earlier one.9United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 1490 – Disclaimers
A terminal disclaimer also requires that both patents stay under common ownership for the later one to remain enforceable. If ownership splits, the disclaimed patent becomes unenforceable.10United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 804 – Definition of Double Patenting Anyone acquiring patents should check for attached disclaimers, because they affect both the expiration date and whether the patent can be enforced at all.
Calculating a Specific Patent’s Expiration Date
Pinning down the actual expiration date takes more than adding 20 years to a filing date. Start by identifying the patent type and the correct anchor date. For a utility or plant patent, that is the earliest US non-provisional filing date in the priority chain. For a design patent, add 15 years to the grant date. Then layer on any modifications:
- PTA days, listed on the front page of the patent, are added to the base expiration date.
- PTE days are also printed on the patent and recorded in the USPTO’s list of extended patents.
- A terminal disclaimer ties the expiration to an earlier patent’s date, so the earlier patent’s expiration has to be calculated too.
- Confirm that all three maintenance fees were paid on time. If any were missed, the patent may already have lapsed.
The USPTO offers a downloadable patent term calculator for estimates, though the office notes it does not officially compute expiration dates for individual patents. The underlying records, including filing history, PTA and PTE data, and fee payment status, are available through Patent Center.11United States Patent and Trademark Office. Patent Term Calculator
Reinstating a Patent That Lapsed for Nonpayment
A patent that expired because of a missed maintenance fee is not necessarily gone permanently. The owner can petition the USPTO to accept a late payment, but the petition must show that the entire delay was unintentional.12eCFR. 37 CFR 1.378 – Acceptance of Delayed Maintenance Fees in Expired Patents
The filing includes the overdue maintenance fee, a petition fee, and a signed unintentional-delay statement. If the patent has been expired for more than two years, the USPTO requires a detailed explanation of why the delay happened and why it qualifies.13United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2590 – Acceptance of Delayed Payment of Maintenance Fee in Expired Patent Choosing not to pay because you questioned the patent’s value, or deliberately deferring for financial reasons, does not qualify.
Reinstatement comes with a catch. Anyone who started making, importing, or using the invention during the lapse has intervening rights to keep doing so. A court can also let parties who made substantial preparation during the lapse continue under terms the court finds fair.14United States Patent and Trademark Office. Manual of Patent Examining Procedure Section 2591 – Intervening Rights in Reinstated Patents The patent returns, but competitors who acted in good faith during the lapse cannot be shut out.
What Expiration Actually Frees
Once a patent expires, the invention enters the public domain. Anyone can make, sell, or use the technology without a license, and royalty obligations tied to the patent’s claims end. The Supreme Court has held that requiring royalties for use of a patented invention after expiration is unlawful.
Expiration frees only what the patent’s claims covered. The brand name may still be a registered trademark, the manual may be copyrighted, and related trade secrets can remain enforceable. For pharmaceuticals, FDA regulatory exclusivity may continue blocking generic entry after the patent term ends. Checking patent status alongside the FDA’s Orange Book and the broader intellectual property picture is the only reliable way to know what a competitor can actually do.