When does a US patent expire? How to work it out

A US utility patent filed on or after June 8, 1995 normally expires 20 years after the filing date of the earliest US non-provisional application it claims benefit from. Patent term adjustment can push that date later, a terminal disclaimer can pull it earlier, a regulatory extension can add time, and an unpaid maintenance fee can end the patent years before any of these dates. To get the real answer, check each factor in turn.

The steps below run one hypothetical patent through the whole calculation. The rules are in 35 U.S.C. § 154, and the USPTO's practice is set out in MPEP 2701.

Step 1: Find the start date

Under § 154(a)(2), the term ends 20 years from the application's filing date. If the patent claims the benefit of earlier US non-provisional applications under § 120, § 121 or § 365(c), the 20 years run from the filing date of the earliest of them. Continuations, divisionals and continuations-in-part all count from that earliest application, so a patent granted years after its parent can have the same nominal end date.

The benefit claims are listed under the related US application data on the face of the patent. Confirm them in the file history, since a long chain can have several links and the first page is easy to misread.

Example. Our hypothetical patent is a continuation filed 10 June 2014. It claims the benefit of a parent application filed 30 April 2010. The start date is 30 April 2010.

Step 2: Ignore provisional and foreign priority

Section 154(a)(3) excludes priority under § 119, § 365(a) and § 365(b) from the term calculation. That covers US provisional applications and foreign applications alike. Both can matter a great deal for prior-art dates, but neither moves the expiry.

Example. The parent claimed priority to a US provisional filed 2 May 2009 and to a foreign application. Neither counts. Twenty years from 30 April 2010 gives a nominal expiry of 30 April 2030.

Less common situations, such as applications that entered the US as the national stage of an international application, are covered in MPEP 2701.

Step 3: Add patent term adjustment

Section 154(b) adds days to the term to compensate for certain USPTO delays during examination, less certain delays attributed to the applicant. The face of the patent states the number of days by which the term is extended or adjusted. Check the file as well, because the figure can be corrected after grant.

Adjustment belongs to each patent separately. A continuation does not inherit its parent's adjustment. It has its own figure, based on its own examination.

Example. The continuation's face shows 212 days of adjustment. Adding 212 days to 30 April 2030 gives 28 November 2030.

Step 4: Check for a terminal disclaimer

A terminal disclaimer gives up the part of a patent's term that would run past the term of a reference patent, usually to overcome an obviousness-type double patenting rejection. Under 37 C.F.R. § 1.321, a terminally disclaimed patent expires no later than the reference patent. The face of the patent usually notes that it is subject to a terminal disclaimer. The disclaimer itself, which names the reference patent, is in the file history.

This is the step most often missed, and it can cancel the adjustment from step 3. A patent capped at its parent's expiry gains nothing from adjustment days that would run past that cap.

Example. The continuation is subject to a terminal disclaimer over its parent. The parent received no adjustment and expires 30 April 2030. The continuation therefore expires no later than 30 April 2030, and its 212 days of adjustment have no effect.

Step 5: Check maintenance fee status

A utility patent stays in force only while its maintenance fees are paid. Under 35 U.S.C. § 41(b), fees fall due 3.5, 7.5 and 11.5 years after grant, with a six-month grace period on payment of a surcharge. If a fee is still unpaid when the grace period ends, the patent expires.

Example. The continuation was granted 12 January 2016, so its fees fell due on 12 July 2019, 12 July 2023 and 12 July 2027, each with a grace period running six months beyond. The owner paid the first two but not the third. The patent expired at the end of that grace period, on 12 January 2028, more than two years before the date from step 4.

A lapse is not always final. Under 37 C.F.R. § 1.378, the owner can petition to reinstate a patent whose fee was not paid if the delay was unintentional. Read the USPTO's fee and petition records directly, and treat a recent lapse as possibly temporary.

Step 6: Check for a § 156 extension

For patents on products that needed regulatory review before marketing, such as drugs and some medical devices, 35 U.S.C. § 156 provides a term extension for time lost to that review, for example during FDA approval. The extension can be up to five years, and the remaining term after approval cannot exceed 14 years.

An extension is granted after the patent issues, on application, so it does not appear in the original grant. Look for an extension certificate in the file. How an extension combines with the other factors depends on the facts, so treat any patent that has one as a case for careful review.

Example. Our hypothetical patent did not go through regulatory review, so this step changes nothing.

Step 7: Use the older rule for pre-June 8, 1995 patents

Under § 154(c)(1), a patent that was in force on June 8, 1995, or that issued on an application filed before that date, runs for the greater of 20 years from filing or 17 years from grant. Almost all of these patents have now expired. The rule still matters when you need to know whether an older patent was in force on a particular past date, for example when reviewing a historical license or damages period.

Example. A hypothetical application filed 1 March 1994 was granted 5 August 1997. Twenty years from filing is 1 March 2014; 17 years from grant is 5 August 2014. The later date applies: 5 August 2014, subject to fee status and any terminal disclaimer.

Design patents use a different clock

Design patents are governed by 35 U.S.C. § 173. For applications filed on or after May 13, 2015, the term is 15 years from the date of grant, not from filing. Older design patents had a 14-year term from grant. The maintenance fees in § 41(b) apply to utility patents; design patents do not carry them.

The factors in one table

Common mistakes

• Counting from a provisional or foreign priority date. Section 154(a)(3) excludes it, and using it usually produces an expiry up to a year too early.
• Treating a database's projected expiry as final. Projections often leave out terminal disclaimers, later adjustment corrections or fee lapses.
• Treating family members as independent. Continuations share the start date, and terminal disclaimers often tie several members to the same reference patent.
• Treating a lapsed patent as permanently gone. Reinstatement is available if the delay was unintentional.

Why the date matters

Expiry decides whether a patent belongs in a freedom-to-operate review at all, how long a license needs to run, and how much remaining value a portfolio carries. Step 5 of our freedom-to-operate checklist depends on exactly this calculation.

One Transform's Freedom to Operate search looks for in-force patents that could read on a product's features and scores each blocking candidate for risk. For any patent that ends up near the top of that list, confirm its expiry with the steps above before deciding whether to license, design around, challenge or monitor.

Next step

Run a Freedom to Operate search on your next product at onetransform.ai, then work through these seven steps for each patent at the top of the results.

This article is general information about patent practice, not legal advice. For advice on a specific matter, consult a registered patent attorney or agent.