MPEP § 1878.01(a) — Prior Art for Purposes of the Written Opinion and the International Preliminary Examination Report (Annotated Rules)

§1878.01(a) Prior Art for Purposes of the Written Opinion and the International Preliminary Examination Report

USPTO MPEP version: BlueIron's Update: 2025-12-31

This page consolidates and annotates all enforceable requirements under MPEP § 1878.01(a), including statutory authority, regulatory rules, examiner guidance, and practice notes. It is provided as guidance, with links to the ground truth sources. This is information only, it is not legal advice.

Prior Art for Purposes of the Written Opinion and the International Preliminary Examination Report

This section addresses Prior Art for Purposes of the Written Opinion and the International Preliminary Examination Report. Contains: 2 requirements, 1 permission, and 4 other statements.

Key Rules

Topic

Article 19 Amendment Scope

3 rules
StatutoryInformativeAlways
[mpep-1878-01-a-82b0fee74db7a76dd2ffd2de]
Priority Claim Valid Within Two Months
Note:
If an international application claims priority and has a filing date later than the priority period but within two months, the earlier application’s filing date is valid unless the International Preliminary Examining Authority deems the claim invalid for other reasons.

(b) For the purposes of paragraph (a), the relevant date shall be:

(iii) where the international application under international preliminary examination claims the priority of an earlier application and has an international filing date which is later than the date on which the priority period expired but within the period of two months from that date, the filing date of such earlier application, unless the International Preliminary Examining Authority considers that the priority claim is not valid for reasons other than the fact that the international application has an international filing date which is later than the date on which the priority period expired.

Jump to MPEP SourceArticle 19 Amendment ScopeArticle 19 Amendment TimingPCT Claims Format
StatutoryInformativeAlways
[mpep-1878-01-a-97f7d9489789590bbd3ba279]
Priority Claim Validity Within Two Months
Note:
The filing date of an earlier application is used as the relevant date for prior art if the international application claims priority and has a later international filing date, provided it falls within two months after the priority period expired.

The relevant date for the purpose of considering prior art is defined in PCT Rule 64.1(b) as:

(C) where the international application claims the priority of an earlier application and has an international filing date which is later than the date on which the priority period expired but within the period of two months from that date, the filing date of such earlier application, unless the Authority considers that the priority claim is not valid for reasons other than the fact that the international application has an international filing date which is later than the date on which the priority period expired.

Jump to MPEP SourceArticle 19 Amendment ScopeArticle 19 Amendment TimingPCT Claims Format
StatutoryRequiredAlways
[mpep-1878-01-a-b07a937d87157f493549238f]
Claimed Priority Date Must Be Valid for Relevant Date Determination
Note:
Examiner must assess if the claimed priority date is valid when a relevant document was published between the priority date and international filing date.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourceArticle 19 Amendment ScopeInternational Filing DateInterviews in National Stage
Topic

Patent Cooperation Treaty

3 rules
StatutoryInformativeAlways
[mpep-1878-01-a-e45154b1acc477d50ca20a72]
Requirement for Written Opinion of International Searching Authority
Note:
The rule requires the written opinion of the International Searching Authority to be provided in accordance with PCT Rule 43bis.1(b).

The above provisions apply mutatis mutandis to the written opinion of the International Searching Authority. See PCT Rule 43bis.1(b).

Jump to MPEP SourcePatent Cooperation TreatyInternational Searching Authority (ISA)Written Opinion of ISA
StatutoryInformativeAlways
[mpep-1878-01-a-dda1469590c2c9362a12819c]
PCT Rule for Determining Relevant Prior Art Date
Note:
Defines the date used to assess prior art in PCT applications, considering filing dates and priority claims.
The relevant date for the purpose of considering prior art is defined in PCT Rule 64.1(b) as:
  • (A) the international filing date (subject to (B) and (C));
  • (B) where the international application claims the priority of an earlier application and has an international filing date which is within the priority period, the filing date of such earlier application, unless the Authority considers that the priority claim is not valid;
  • (C) where the international application claims the priority of an earlier application and has an international filing date which is later than the date on which the priority period expired but within the period of two months from that date, the filing date of such earlier application, unless the Authority considers that the priority claim is not valid for reasons other than the fact that the international application has an international filing date which is later than the date on which the priority period expired.
Jump to MPEP SourcePatent Cooperation TreatyArticle 19 Amendment ScopeArticle 19 Amendment Timing
StatutoryInformativeAlways
[mpep-1878-01-a-c6dda68632bc70719b888035]
Requirement for Oral Disclosure Under PCT Rules
Note:
The rule requires that oral or non-written disclosure must comply with PCT Rules 64.2 and 70.9.

For oral or non-written disclosure, see PCT Rules 64.2 and 70.9.

Jump to MPEP SourcePatent Cooperation Treaty
Topic

Article 34 Amendments

2 rules
StatutoryPermittedAlways
[mpep-1878-01-a-9d8ba7385b7deb0c1ae493db]
Claimed Priority Date Requirement for Relevant Documents
Note:
The examiner must consider the validity of the claimed priority date when a document is published between the priority and filing dates, especially after April 1, 2007.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourceArticle 34 AmendmentsInternational Searching Authority (ISA)Search in National Stage
StatutoryInformativeAlways
[mpep-1878-01-a-11299ef39716d40afa73e079]
Published Applications Not Considered Prior Art After Relevant Date
Note:
Documents published after the relevant date but filed earlier are not considered prior art for international preliminary examination.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourceArticle 34 AmendmentsInternational Search ReportSearch in National Stage
Topic
1 rules
StatutoryRequiredAlways
[mpep-1878-01-a-4623e35808ea4dddefa61f33]
Relevant Date for Prior Art Search
Note:
Determines the date used to identify prior art for national stage examination, prioritizing international filing date, priority claim, or specific period conditions.
(b) For the purposes of paragraph (a), the relevant date shall be:
  • (i) subject to items (ii) and (iii), the international filing date of the international application under international preliminary examination;
  • (ii) where the international application under international preliminary examination claims the priority of an earlier application and has an international filing date which is within the priority period, the filing date of such earlier application, unless the International Preliminary Examining Authority considers that the priority claim is not valid;
  • (iii) where the international application under international preliminary examination claims the priority of an earlier application and has an international filing date which is later than the date on which the priority period expired but within the period of two months from that date, the filing date of such earlier application, unless the International Preliminary Examining Authority considers that the priority claim is not valid for reasons other than the fact that the international application has an international filing date which is later than the date on which the priority period expired.
Jump to MPEP SourceSearch in National StageArticle 19 Amendment ScopeArticle 19 Amendment Timing
Topic

International Searching Authority (ISA)

1 rules
StatutoryInformativeAlways
[mpep-1878-01-a-2024286126d23cbbd6fa0ae5]
Written Opinion Requirement for ISA
Note:
The rule requires that the provisions apply similarly to the written opinion of the International Searching Authority.

The above provisions apply mutatis mutandis to the written opinion of the International Searching Authority. See PCT Rule 43bis.1(b).

Jump to MPEP SourceInternational Searching Authority (ISA)Written Opinion of ISAInternational Search
Topic

Article 19 Amendment Timing

1 rules
StatutoryRecommendedAlways
[mpep-1878-01-a-327fb034697166f2e8d7fc39]
Priority Date Valid Within Two Months After Expiration
Note:
A priority date is valid for international applications filed within two months after the expiration of the priority period, provided they are filed on or after April 1, 2007.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourceArticle 19 Amendment TimingPriority Claim in PCTPCT Application as 102(a)(2) Prior Art
Topic

PCT Claims Format

1 rules
StatutoryInformativeAlways
[mpep-1878-01-a-3017a5fd0f98fdae659df7d5]
Claimed Priority Date Determines Relevant Date for Written Opinion
Note:
The 'relevant date' for the written opinion is based on the claimed priority date if there's insufficient time for the examiner to make a proper determination.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourcePCT Claims FormatInternational Searching Authority (ISA)Written Opinion of ISA
Topic

International Preliminary Examining Authority (IPEA)

1 rules
StatutoryInformativeAlways
[mpep-1878-01-a-503aab8ca2511fd76e5b4266]
Certain Published Documents Must Be Listed on PCT Forms
Note:
Documents published between the priority date and international filing date must be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409 under 'CERTAIN PUBLISHED DOCUMENTS'.

When a potentially relevant document has been published between a claimed priority date of the application and its international filing date, the examiner is required to consider whether the claimed priority date is valid for the purposes of determining the "relevant date" of the claims in the international application. For international applications filed on or after April 1, 2007, a priority date should not be considered invalid merely because the international application was not filed prior to the date of expiration of the priority period, provided that the international application is filed within the period of two months from the date of expiration of the priority period. Note that if there is time left for the applicant to perfect, correct or add a priority claim but there is insufficient time for the examiner to make a proper determination as to whether the priority claim is valid, due to the need to issue a timely written opinion by the International Searching Authority, the "relevant date" for the purposes of the written opinion will be based on the claimed priority date. See Chapter 11 of the International Search and Preliminary Examination Guidelines, which may be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html). In cases where any application or any patent which would constitute prior art for the purpose of international preliminary examination as to novelty and inventive step (nonobviousness) was published on or after the relevant date of the international application under consideration but was filed earlier than the relevant date or claimed the priority of an earlier application which was filed prior to the relevant date, the published application or patent is not to be considered part of the prior art for the purpose of international preliminary examination as to novelty and inventive step. Nevertheless, these documents are to be listed on Form PCT/ISA/237, PCT/IPEA/408, or PCT/IPEA/409, as appropriate under the heading “CERTAIN PUBLISHED DOCUMENTS”.

Jump to MPEP SourceInternational Preliminary Examining Authority (IPEA)International Searching Authority (ISA)Request Content and Form

Citations

Primary topicCitation
International Searching Authority (ISA)
Patent Cooperation Treaty
PCT Rule 43bis.1(b)
Article 19 Amendment Scope
Patent Cooperation Treaty
PCT Rules 64.2

Source Text from USPTO’s MPEP

This is an exact copy of the MPEP from the USPTO. It is here for your reference to see the section in context.

BlueIron Last Updated: 2025-12-31