35 U.S.C. · Part IV · Chapter 37, National stage
35 U.S.C. 371: National stage: Commencement
In plain English
Section 371 governs how a PCT international application designating the United States becomes a US application. The national stage begins when the time limit under PCT Article 22 or 39 expires (section 371(b)), which for the US is 30 months from the priority date (37 CFR 1.495). It can begin earlier if the applicant expressly asks and has met the requirements (section 371(f)).
To enter, the applicant must file the basic national fee and, unless the International Bureau has already sent it, a copy of the international application. Under 37 CFR 1.495(b) both are due by 30 months from priority; if they are missing at that date, the application is abandoned as to the US. Other items can follow within a period the USPTO sets, with a surcharge: an English translation if the application was filed in another language, the inventors' oath or declaration, and the search and examination fees.
Article 19 amendments made in the international phase must be filed (or already communicated by the International Bureau), with a translation if needed, by the start of the national stage or they are treated as canceled. After entry, the applicant can amend the specification, claims and drawings, and the application is examined under US law with one difference: unity of invention, not US restriction practice, governs how many inventions can stay in the case (37 CFR 1.499).
Annotation by Raj Sutariya, Co-founder, PatentAssist.ai. General information, not legal advice; the statute below governs.
Text of 35 U.S.C. 371
Current text, quoted from the official United States Code.
(a) Receipt from the International Bureau of copies of international applications with any amendments to the claims, international search reports, and international preliminary examination reports including any annexes thereto may be required in the case of international applications designating or electing the United States.
(b) Subject to subsection (f) of this section, the national stage shall commence with the expiration of the applicable time limit under article 22(1) or (2), or under article 39(1)(a) of the treaty.
(c) The applicant shall file in the Patent and Trademark Office—
(1) the national fee provided in section 41(a);
(2) a copy of the international application, unless not required under subsection (a) of this section or already communicated by the International Bureau, and a translation into the English language of the international application, if it was filed in another language;
(3) amendments, if any, to the claims in the international application, made under article 19 of the treaty, unless such amendments have been communicated to the Patent and Trademark Office by the International Bureau, and a translation into the English language if such amendments were made in another language;
(4) an oath or declaration of the inventor (or other person authorized under chapter 11) complying with the requirements of section 115 and with regulations prescribed for oaths or declarations of applicants;
(5) a translation into the English language of any annexes to the international preliminary examination report, if such annexes were made in another language.
(d) The requirements with respect to the national fee referred to in subsection (c)(1), the translation referred to in subsection (c)(2), and the oath or declaration referred to in subsection (c)(4) of this section shall be complied with by the date of the commencement of the national stage or by such later time as may be fixed by the Director. The copy of the international application referred to in subsection (c)(2) shall be submitted by the date of the commencement of the national stage. Failure to comply with these requirements shall be regarded as abandonment of the application by the parties thereof. The payment of a surcharge may be required as a condition of accepting the national fee referred to in subsection (c)(1) or the oath or declaration referred to in subsection (c)(4) of this section if these requirements are not met by the date of the commencement of the national stage. The requirements of subsection (c)(3) of this section shall be complied with by the date of the commencement of the national stage, and failure to do so shall be regarded as a cancellation of the amendments to the claims in the international application made under article 19 of the treaty. The requirement of subsection (c)(5) shall be complied with at such time as may be fixed by the Director and failure to do so shall be regarded as cancellation of the amendments made under article 34(2)(b) of the treaty.
(e) After an international application has entered the national stage, no patent may be granted or refused thereon before the expiration of the applicable time limit under article 28 or article 41 of the treaty, except with the express consent of the applicant. The applicant may present amendments to the specification, claims and drawings of the application after the national stage has commenced.
(f) At the express request of the applicant, the national stage of processing may be commenced at any time at which the application is in order for such purpose and the applicable requirements of subsection (c) of this section have been complied with.
Practical notes
Instead of entering under section 371, an applicant can file a new application under section 111(a) claiming the benefit of the PCT application under sections 120 and 365(c), often called a bypass continuation. It must be filed while the PCT application is still pending. It allows a fresh specification or claims, and US restriction practice applies instead of unity (MPEP 1895 and 1896).
If the 30-month date is missed, the application can be revived by petition under 37 CFR 1.137 if the delay was unintentional. For petitions filed after August 13, 2026, a delay of more than one year also needs an explanation of the circumstances. Diary 30 months from the earliest priority date, not from the PCT filing date.
Use the international search and any written opinion. Amending the claims at national stage entry to meet the cited art, before the first US action, often shortens prosecution. Patent term adjustment for over-3-year pendency runs from the date the national stage commenced (section 154(b)(1)(B)).
Related rules and guidance
- 37 CFR
- § 1.491, § 1.492, § 1.495, § 1.496, § 1.497, § 1.499
- MPEP
- 1893, 1895, 1896
Read next
- 35 U.S.C. 115: Inventor's oath or declaration
- 35 U.S.C. 119: Priority and provisional benefit
- 35 U.S.C. 120: Continuing applications
- 35 U.S.C. 154: Patent term and adjustment
- 35 U.S.C. 184: Foreign filing license
- Entering the US national stage under 35 U.S.C. 371
- The PCT application: timeline, fees and national phase
- USPTO patent fees (2026)
All annotated sections of 35 U.S.C.
Statute text from the United States Code published by the Office of the Law Revision Counsel of the U.S. House of Representatives (uscode.house.gov). Text contains those laws in effect through Public Law 119-124 (October 15, 2026). Editorial notes and footnotes are omitted. The annotations are general information, not legal advice; check the official text and a registered patent practitioner before relying on them.