Patent Term Adjustment (PTA): What It Is and How It Is Calculated

A patent’s term begins on the day it issues and ends 20 years from the date the application was filed in the United States or, if it claims the benefit of earlier applications under 35 U.S.C. § 120, 121, 365(c) or 386(c), from the earliest of those filing dates (§ 154(a)(2)). Priority claims under § 119, 365(a)-(b) or 386(a)-(b) are not taken into account (§ 154(a)(3)). Section 154(b) restores time lost to Office delay through three "patent term guarantees."

The USPTO’s rules implementing PTA (37 C.F.R. §§ 1.702-1.705) apply only to original applications, except design applications, filed on or after May 29, 2000, and the patents issued on them.

Sources: 35 U.S.C. § 154(a)-(b); 37 C.F.R. § 1.702(f); MPEP § 2730.

This guide calls the three guarantees "A delay," "B delay" and "C delay," after the subparagraphs of § 154(b)(1) that create them. Each adds one day of term for each day of the delay it measures.

• RCE time and B delay. The rule excludes from B delay the period from the filing of any RCE to the mailing of the notice of allowance (§ 1.703(b)(1)). The MPEP notes the Federal Circuit’s holding in Novartis AG v. Lee (2014) that time consumed by continued examination does not include the time after a notice of allowance is mailed, unless the Office actually resumes examination.
• Successful appeals and C delay. According to the MPEP, there is no "reversal of an adverse determination of patentability" if the examiner reopens prosecution after the appeal brief instead of answering it (Chudik v. Hirshfeld, Fed. Cir. 2021), and the claim that issues must not differ substantively from the claim reviewed on appeal (SawStop Holding v. Vidal, Fed. Cir. 2022).
• Continuing applications. PTA does not include any period before the actual filing date of the application that became the patent (§ 1.704(c)(14)). A continuation starts its own A and B clocks.

Sources: 35 U.S.C. § 154(b)(1); 37 C.F.R. § 1.702, § 1.703, § 1.704(c)(14); MPEP §§ 2730, 2731.

Adjustment is reduced by "a period equal to the period of time during which the applicant failed to engage in reasonable efforts to conclude prosecution" (§ 154(b)(2)(C)(i)). The statute fixes one rule itself, and the USPTO’s regulation lists the rest.

The three-month rule. Any time beyond three months taken to reply to an Office notice or action making a rejection, objection, argument or other request is applicant delay, counted from the day after the three-month date until the reply is filed (§ 1.704(b)). The shortened statutory period set in the action does not matter: a reply filed in month four with a paid extension still costs about a month of PTA. The filing date of the reply counts, not the date on a certificate of mailing (§ 1.703(f)).

The IDS safe harbor. An IDS filed alone, or an RCE whose only submission is an IDS, is not treated as applicant delay under § 1.704(c)(6), (8), (9), (10) or (12) if it is accompanied by a statement that each item was first cited in, or is, a communication from the USPTO or a patent office in a counterpart foreign or international application that no one with the duty of disclosure received more than 30 days before the IDS was filed. The 30 days cannot be extended, and the statement must be made on Form PTO/SB/133 (§ 1.704(d)). A statement under § 1.97(e), used for IDS timing, does not substitute for it (MPEP § 609.04(b)(V)).

What the Federal Circuit has said about applicant delay:

• Gilead Sciences v. Lee (2015): a supplemental IDS filed after a reply to a restriction requirement was applicant delay under § 1.704(c)(8), whether or not it caused actual delay.
• Supernus Pharmaceuticals v. Iancu (2019): the USPTO "may not count as applicant delay a period of time during which there was no action that the applicant could take to conclude prosecution."
• Intra-Cellular Therapies v. Iancu (2019): a timely after-final response that only kept arguing the merits did not stop the clock; the 21 days until a compliant reply were applicant delay. Per the MPEP, after a final rejection only a reply complying with § 1.113(c), an appeal or an RCE stops it.

Sources: 35 U.S.C. § 154(b)(2)(C); 37 C.F.R. § 1.704, § 1.703(f); MPEP § 2732, § 609.04(b)(V); Gilead Sciences, Inc. v. Lee, 778 F.3d 1341 (Fed. Cir. 2015); Supernus Pharmaceuticals, Inc. v. Iancu, 913 F.3d 1351 (Fed. Cir. 2019); Intra-Cellular Therapies, Inc. v. Iancu, 938 F.3d 1371 (Fed. Cir. 2019).

The adjustment is the sum of the A, B and C periods "to the extent that such periods are not overlapping, less the sum of the periods calculated under § 1.704" (§ 1.703(f)). Where delays overlap, the adjustment "shall not exceed the actual number of days the issuance of the patent was delayed" (§ 154(b)(2)(A)). In Wyeth v. Kappos (Fed. Cir. 2010), the court rejected the USPTO’s earlier reading and held that periods overlap only if they occur on the same calendar days. So, in short:

PTA = A delay + B delay + C delay − days on which they overlap − applicant delay.

A simple illustration (our own numbers): an application gets its first action 300 days after the 14-month date (300 days of A delay). It issues 200 days after its three-year date (200 days of B delay), and 120 of those 200 days also fall within an A delay period. The applicant took one reply 45 days past three months. PTA = 300 + 200 − 120 − 45 = 335 days.

The adjustment runs from the patent’s 20-year expiration date under § 154(a)(2) (§ 1.703(f)). It can never carry a patent past the date in a terminal disclaimer (see below).

Sources: 35 U.S.C. § 154(b)(2)(A); 37 C.F.R. § 1.703(f)-(g); MPEP § 2731, subsection VI (Wyeth v. Kappos, 591 F.3d 1364 (Fed. Cir. 2010)).

• On the patent. "The patent will include notification of any patent term adjustment" (§ 1.705(a)). For patents granted on or after January 14, 2013, the USPTO no longer gives a determination with the notice of allowance; it sends a preliminary calculation with the issue notification, but the number on the patent is the official determination.
• In Patent Center. The calculation is available through the USPTO’s patent electronic filing system. The MPEP encourages applicants to check the recorded type and receipt date of each paper during prosecution and have errors fixed before allowance, because the calculation at grant uses those records.
• If PTA looks too high, a practitioner may say so in a letter; the Office files it without comment. A patentee may also disclaim excess term under 37 C.F.R. § 1.321.

Sources: 37 C.F.R. § 1.705(a); MPEP § 2733; 37 C.F.R. § 1.321.

What the application must say. It must state the correct PTA and its bases under § 1.702; the relevant dates and the adjustment claimed; whether the patent is subject to a terminal disclaimer and its date; and any applicant-delay circumstances under § 1.704, or that there were none (§ 1.705(b)(2)). Reinstatement cannot exceed three additional months for each late reply (§ 1.705(c)). The same procedure applies whether the patentee thinks the PTA is too low or too high.

What the Office does. It recalculates by hand and grants the request (with a certificate of correction), denies it, or issues a redetermination or requirement for information that allows a renewed request within two months (extendable, no further fee).

Going to court. Only after a decision denying reconsideration may the patentee sue the Director in the U.S. District Court for the Eastern District of Virginia, the "exclusive remedy," within 180 days of that decision. The deadline is strictly applied: in Guymon v. Squires (Fed. Cir. Sept. 10, 2026, nonprecedential), the court affirmed dismissal of a complaint received two days after the 180-day deadline. Third parties may not challenge a PTA determination before the patent is granted (§ 154(b)(4)(B)), and the Office will not consider third-party papers about PTA (§ 1.705(d)).

Sources: 35 U.S.C. § 154(b)(3)-(4); 37 C.F.R. § 1.705; 37 C.F.R. § 1.18(e)-(f); USPTO fee schedule; MPEP § 2734; Guymon v. Squires, No. 2025-1542 (Fed. Cir. Sept. 10, 2026).

"No patent the term of which has been disclaimed beyond a specified date may be adjusted under this section beyond the expiration date specified in the disclaimer" (§ 154(b)(2)(B)). A terminal disclaimer filed to overcome an obviousness-type double patenting (ODP) rejection usually ties the patent to the expiration of an earlier family patent, so PTA on the later patent is cut off at that date.

• In re Cellect (Fed. Cir. 2023): "ODP for a patent that has received PTA, regardless whether or not a terminal disclaimer is required or has been filed, must be based on the expiration date of the patent after PTA has been added." Claims of Cellect’s later-expiring family patents were held unpatentable in reexamination, and because the patents had expired, a terminal disclaimer could not cure it.
• Allergan USA v. MSN Laboratories (Fed. Cir. 2024): "a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim having a common priority date." A parent patent keeps its PTA even if a continuation with less PTA issues later.

In practice, PTA earned by a later continuation in the same family is the PTA most at risk, either through a terminal disclaimer or an ODP challenge.

Sources: 35 U.S.C. § 154(b)(2)(B); 37 C.F.R. § 1.703(g), § 1.321; In re Cellect, LLC, 81 F.4th 1216 (Fed. Cir. 2023); Allergan USA, Inc. v. MSN Laboratories Private Ltd., No. 2024-1061 (Fed. Cir. Aug. 13, 2024). The last paragraph is our own reading of those decisions, not legal advice.

Patent term extension under 35 U.S.C. § 156 is a different remedy for a different delay: time lost to regulatory review before a product (for example, a human drug product) can be marketed.

Sources: 35 U.S.C. § 156(a), (c), (d)(1), (g)(6)(A); 35 U.S.C. § 154(b); In re Cellect, LLC (Fed. Cir. 2023).

1. Treating extensions of time as free: every day past three months reduces PTA.
2. Filing papers after a reply or after allowance without counting the cost, or an IDS without the § 1.704(d) statement when it qualifies.
3. Leaving the application incomplete past 8 months.
4. Arguing the merits after a final rejection instead of filing a compliant reply, appeal or RCE.
5. Missing the two-month window after grant, or the 180-day window to sue.
6. Forgetting that a terminal disclaimer caps PTA and that ODP uses PTA-adjusted dates.

Sources: 37 C.F.R. §§ 1.704, 1.705; 35 U.S.C. § 154(b)(2)(B), (b)(4); Intra-Cellular Therapies v. Iancu (Fed. Cir. 2019); In re Cellect (Fed. Cir. 2023). More on prosecution, with the latest decisions on each patentability requirement, is on our patent prosecution hub.