35 U.S.C. § 154 (Patent Term)

35 U.S.C. § 154, titled ‘Contents and term of patent; provisional rights,’ is the U.S. Patent Act provision that does two distinct things: it defines what a patent actually grants (the exclusionary right), and it fixes how long that grant lasts, including a mechanism — patent term adjustment (PTA) — for extending term when the USPTO itself causes delay during examination. It is the statutory anchor for the commonly-cited ‘patents last 20 years’ rule, and the reason that rule is an approximation rather than a fixed number for any specific patent.

The right granted — § 154(a)(1)

Section 154(a)(1) states that every patent contains a grant to the patentee of ‘the right to exclude others from making, using, offering for sale, or selling the invention throughout the United States or importing the invention into the United States’ — and, where the invention is a process, a parallel right to exclude others from using, offering for sale, or selling products made by that process. This is the legal core of what a patent actually is: not an affirmative right to practice the invention oneself (an inventor can still be blocked by someone else’s earlier, broader patent), but a right to stop others. It is the statutory basis for the shorthand definition used throughout CASRAI’s patent content — see utility patent and trademark for how this exclusionary right differs from other IP protections.

The term — § 154(a)(2)

Section 154(a)(2) sets the term of a utility or plant patent at 20 years from the filing date of the earliest U.S. non-provisional application in the patent’s priority chain — specifically, the earliest application to which the patent claims benefit under sections 120, 121, 365(c), or 386(c) (continuations, divisionals, and certain national-stage/international claims). Two details matter for research administrators and inventors alike:

• A provisional application does not start the clock. Foreign and provisional priority claimed under sections 119, 365(a), 365(b), 386(a), or 386(b) is explicitly excluded from the term calculation. Filing a 12-month provisional first, then converting to a non-provisional, does not shorten the eventual 20-year term — term runs from the non-provisional filing date, not the provisional one. See provisional patent applications for how the provisional-to-non-provisional pathway works.
• Continuations and divisionals do not reset the clock. Because term is measured from the earliest application in the chain, filing a continuation or divisional years into prosecution does not grant a fresh 20 years — it inherits the original filing date’s term, which is already running down.

Design patents are governed by a separate provision, 35 U.S.C. § 173 (15 years from grant, not filing, for applications filed on or after May 13, 2015), and are unaffected by § 154’s 20-year rule. See How Long Do Patents Last? for the full practical breakdown across utility, design, and plant patents, including maintenance-fee deadlines that run independently of term.

Patent term adjustment (PTA) — § 154(b)

Section 154(b), added by the American Inventors Protection Act of 1999, authorizes the USPTO to add days back onto a patent’s 20-year term when the agency itself is responsible for prosecution delay. PTA is calculated under three overlapping guarantee categories:

• ‘A’ delay — the USPTO misses a specific prosecution deadline, such as issuing a first office action within 14 months of filing.
• ‘B’ delay — the patent does not issue within 3 years of the actual filing date, with time consumed by requests for continued examination (RCEs), secrecy orders, interferences, and successful applicant appeals excluded from that 3-year count.
• ‘C’ delay — delay caused by interference proceedings, a secrecy order, or a successful appeal, with no statutory cap on the days that can accrue.

Overlapping days across categories are counted only once, not stacked. PTA is also reduced for periods of applicant delay — most commonly, taking longer than three months to respond to an office action — and filing an RCE cuts off further ‘B’-guarantee accrual from that point forward. The net effect is that two patents filed the same day, in the same family, can have different actual expiration dates once PTA is applied; the docketed expiration date on an issued patent (not a flat ‘filing date plus 20 years’ calculation) is the one that governs enforcement.

PTA is distinct from patent term extension (PTE) under 35 U.S.C. § 156, which compensates for regulatory-review delay (chiefly FDA review) rather than USPTO examination delay, and applies only to patents covering products subject to that review. A single patent can in principle receive both PTA and PTE. See How Long Do Patents Last? for the PTE mechanics and the current maintenance-fee schedule.

Why § 154 matters for research administration and tech transfer

For a university technology transfer office, § 154 determines the real commercial runway a licensee is actually buying. A license negotiated late in prosecution, or covering a continuation filed years after the parent application, inherits a term that is already partway spent — the licensee is not getting 20 fresh years from the license execution date. PTA figures (published on the face of every issued patent, alongside the calculated expiration date) should be checked directly rather than assumed, since USPTO-side delay is common and PTA amounts vary patent-by-patent even within the same family.

Related statutory provisions

§ 154 works alongside, but is legally distinct from, the other core Patent Act provisions governing what can be patented and how a granted patent is defended: 35 U.S.C. § 101 (subject-matter eligibility), 35 U.S.C. § 102 (novelty), 35 U.S.C. § 112 (specification, enablement, and definiteness), and 35 U.S.C. § 282 (presumption of validity and invalidity defenses in litigation). None of those provisions affects how long a patent’s term runs — only § 154 (and, for design patents, § 173) does that.

Frequently asked questions

How long does a U.S. utility patent last?

Generally 20 years from the filing date of the earliest non-provisional application in its priority chain, under 35 U.S.C. § 154(a)(2), adjusted up or down by any patent term adjustment under § 154(b) and reduced by any terminal disclaimer filed during prosecution.

Does filing a provisional application shorten a patent’s term?

No. Provisional priority is explicitly excluded from the § 154(a)(2) term calculation, so term runs from the later non-provisional filing date, not the earlier provisional one.

What is patent term adjustment (PTA)?

Additional days added to a patent’s term under 35 U.S.C. § 154(b) to compensate for specific categories of USPTO-caused prosecution delay — separate from patent term extension (PTE) under § 156, which compensates for regulatory-review delay.

Where do I find a specific patent’s actual expiration date?

The issued patent itself states its calculated PTA (if any) on its face; the true expiration date is the base 20-year term as adjusted by PTA and reduced by any terminal disclaimer — not a flat filing-date-plus-20-years calculation.