MPEP § 1875.01 — Preparation of Invitation Concerning Unity (Annotated Rules)

§1875.01 Preparation of Invitation Concerning Unity

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

This page consolidates and annotates all enforceable requirements under MPEP § 1875.01, 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.

Preparation of Invitation Concerning Unity

This section addresses Preparation of Invitation Concerning Unity. Primary authority: 37 CFR 1.475. Contains: 5 requirements, 3 guidance statements, and 2 other statements.

Key Rules

Topic

Article 19 Amendment Scope

4 rules
StatutoryRequiredAlways
[mpep-1875-01-6dc2797077809fb12e8009e4]
Requirement for Identifying Linked Inventions
Note:
The examiner must identify and link related inventions using claim numerals on form PCT/IPEA/405, specifying which claims are part of a single inventive concept.

In the space provided on form PCT/IPEA/405, the examiner should identify the disclosed inventions by claim numerals and indicate which disclosed inventions are so linked as to form a single general inventive concept, thereby complying with the requirement of unity of invention. For example, claims to different categories of invention such as a product, claims to a process specifically adapted for the manufacture of the product and a claim for a use of the product would be considered related inventions which comply with the unity of invention requirement, whereas a claim to an apparatus for making the product in the same application would be considered a second invention for which additional fees would be required. The reasons for holding that unity of invention is lacking must be specified. See 37 CFR 1.475 and Chapter 10 of the International Search and Preliminary Examination Guidelines which can be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html).

Jump to MPEP Source · 37 CFR 1.475Article 19 Amendment ScopePCT Claims FormatInternational Preliminary Examining Authority (IPEA)
StatutoryRecommendedAlways
[mpep-1875-01-fa2bd507476488ca98a4dab9]
PCT/IPEA/405 Required for Unity Refusal
Note:
Prepare and mail Form PCT/IPEA/405 if applicant refuses to restrict claims or authorize additional fees.

If applicant refuses to either restrict the claims to one invention or authorize payment of additional fees, or if applicant does not have a deposit account, Form PCT/IPEA/405 should be prepared and mailed to applicant.

Jump to MPEP SourceArticle 19 Amendment ScopeInternational Preliminary Examining Authority (IPEA)Request Content and Form
MPEP GuidanceInformativeAlways
[mpep-1875-01-186b421a384de161feadab94]
Requirement for Inviting Applicant to Restrict Claims or Pay Fees
Note:
The examiner must invite the applicant, at their option, to restrict claims to meet unity of invention requirements or pay additional examination fees and explain why unity is not met.

The “Invitation to restrict or pay additional fees,” Form PCT/IPEA/405, is used to invite the applicant, at his/her option, to restrict the claims to comply with the requirements of unity of invention or to pay additional examination fees. In addition, the examiner must explain the reasons why the international application is not considered to comply with the requirement of unity of invention. The examiner must also specify, on Form PCT/IPEA/405, at least one group or groups of claims which, if elected, would comply with the requirement for unity of invention.

Jump to MPEP SourceArticle 19 Amendment ScopeArticle 34 AmendmentsInternational Preliminary Examining Authority (IPEA)
MPEP GuidanceRequiredAlways
[mpep-1875-01-4010d9eaee27727e382d4ea3]
Examiner Must Specify Claim Groups Compliant with Unity
Note:
The examiner must identify on Form PCT/IPEA/405 at least one group or groups of claims that would comply with the unity of invention requirement.

The “Invitation to restrict or pay additional fees,” Form PCT/IPEA/405, is used to invite the applicant, at his/her option, to restrict the claims to comply with the requirements of unity of invention or to pay additional examination fees. In addition, the examiner must explain the reasons why the international application is not considered to comply with the requirement of unity of invention. The examiner must also specify, on Form PCT/IPEA/405, at least one group or groups of claims which, if elected, would comply with the requirement for unity of invention.

Jump to MPEP SourceArticle 19 Amendment ScopeInternational Preliminary Examining Authority (IPEA)Interviews in National Stage
Topic

Article 34 Amendments

2 rules
StatutoryRequiredAlways
[mpep-1875-01-74a3e093fdc84d998499d3c6]
Reasons for Lack of Unity Must Be Specified
Note:
The examiner must specify the reasons why unity of invention is lacking when making an invitation concerning unity.

In the space provided on form PCT/IPEA/405, the examiner should identify the disclosed inventions by claim numerals and indicate which disclosed inventions are so linked as to form a single general inventive concept, thereby complying with the requirement of unity of invention. For example, claims to different categories of invention such as a product, claims to a process specifically adapted for the manufacture of the product and a claim for a use of the product would be considered related inventions which comply with the unity of invention requirement, whereas a claim to an apparatus for making the product in the same application would be considered a second invention for which additional fees would be required. The reasons for holding that unity of invention is lacking must be specified. See 37 CFR 1.475 and Chapter 10 of the International Search and Preliminary Examination Guidelines which can be obtained from WIPO’s website (www.wipo.int/pct/en/texts/gdlines.html).

Jump to MPEP Source · 37 CFR 1.475Article 34 AmendmentsInternational Searching Authority (ISA)Search in National Stage
StatutoryRequiredAlways
[mpep-1875-01-e48110266e58cce6f963e06b]
Protest Must Be Filed In Writing Within One Month
Note:
Applicants must file any protest in writing within one month of receiving the written opinion or IPER if a lack of unity holding is first mailed with the IPER.

The examiner must further orally advise applicant that any protest to the holding of lack of unity or the amount of additional fee required must be filed in writing no later than one month from the mailing date of the written opinion or the international preliminary examination report if the lack of unity holding is first mailed with the IPER because there was no written opinion. The examiner should fill in the information on Form USPTO/499 “Chapter II PCT Telephone Memorandum for Lack of Unity” as a record of the telephonic holding of lack of unity.

Jump to MPEP SourceArticle 34 AmendmentsInterviews in National StageSignature Requirements
Topic

Filing, Search & Examination Fees

2 rules
StatutoryRecommendedAlways
[mpep-1875-01-aaf69269447b05aff090132f]
Examiner Must Specify Main Invention and Claims to Examine If Fees Not Paid
Note:
If the applicant fails to restrict their claims or pay additional fees, the examiner must specify the main invention and related claims to be examined.

Also, the examiner should specify the main invention and claims directed thereto which will be examined if the applicant fails to restrict or pay additional fees. The main invention, in case of doubt, is the first claimed invention or related invention before the International Preliminary Examining Authority for which a search fee has been paid and an international search report has been prepared.

Jump to MPEP SourceFiling, Search & Examination FeesFee Requirements
StatutoryInformativeAlways
[mpep-1875-01-76975bee988add1c729e9ba1]
Main Invention Claimed First or Related With Search Fee
Note:
The main invention to be examined is the first claimed invention or related one with a paid search fee and an international search report.

Also, the examiner should specify the main invention and claims directed thereto which will be examined if the applicant fails to restrict or pay additional fees. The main invention, in case of doubt, is the first claimed invention or related invention before the International Preliminary Examining Authority for which a search fee has been paid and an international search report has been prepared.

Jump to MPEP SourceFiling, Search & Examination FeesFee Requirements
Topic

Request Content and Form

2 rules
StatutoryInformativeAlways
[mpep-1875-01-ed12b7b19bde30cf72b81c8c]
One Month Response Required
Note:
Respond within one month as per PCT Rule 68.2; extensions are not permitted.

In the box provided at the top of the form, the time limit of one month for response is set according to PCT Rule 68.2. Extensions of time are not permitted.

Jump to MPEP SourceRequest Content and FormPCT Request FormPatent Cooperation Treaty
StatutoryPermittedAlways
[mpep-1875-01-e00a3994cd285e339f6da24c]
Time Limit for Response Not Extendable
Note:
The one-month response time limit set according to PCT Rule 68.2 cannot be extended.

In the box provided at the top of the form, the time limit of one month for response is set according to PCT Rule 68.2. Extensions of time are not permitted.

Jump to MPEP SourceRequest Content and FormPCT Request FormPatent Cooperation Treaty
Topic

International Preliminary Examining Authority (IPEA)

2 rules
StatutoryRecommendedAlways
[mpep-1875-01-214bc498b621ff6b9246fe96]
Supplemental Sheets Required for PCT/IPEA/405
Note:
When the space on Form PCT/IPEA/405 is insufficient, additional sheets supplied by the examiner must be used and referenced to specific sections.

Since the space provided on Form PCT/IPEA/405 is limited, supplemental attachment sheets, supplied by the examiner, with reference back to the specific section, should be incorporated whenever necessary.

Jump to MPEP SourceInternational Preliminary Examining Authority (IPEA)Request Content and FormInternational Preliminary Examination (Chapter II)
StatutoryRequiredAlways
[mpep-1875-01-5fd7913753256392a2b92017]
Examiner With Partial Signatory Authority Must Sign PCT/IPEA/405
Note:
An examiner possessing partial signatory authority is required to sign Form PCT/IPEA/405.

Form PCT/IPEA/405 must be signed by an examiner with at least partial signatory authority.

Jump to MPEP SourceInternational Preliminary Examining Authority (IPEA)Request Content and FormSignatory Authority Review
Topic

Statutory Authority for Examination

1 rules
StatutoryRequiredAlways
[mpep-1875-01-245cc8f518e246fba9c984f2]
Examiner Must Indicate Total Additional Examination Fees
Note:
The examiner is required to specify the total amount of additional fees needed for examining all claimed inventions.

The examiner should indicate the total amount of additional fees required for examination of all claimed inventions.

Jump to MPEP SourceStatutory Authority for ExaminationExamination Procedures
Topic

Demand for Preliminary Examination

1 rules
StatutoryRecommendedAlways
[mpep-1875-01-fb0e0401ebe82e0a0dfc604a]
Examiner Must Record Lack of Unity Holding
Note:
The examiner must fill out Form USPTO/499 to document the telephonic holding of lack of unity and inform applicants about filing protests.

The examiner must further orally advise applicant that any protest to the holding of lack of unity or the amount of additional fee required must be filed in writing no later than one month from the mailing date of the written opinion or the international preliminary examination report if the lack of unity holding is first mailed with the IPER because there was no written opinion. The examiner should fill in the information on Form USPTO/499 “Chapter II PCT Telephone Memorandum for Lack of Unity” as a record of the telephonic holding of lack of unity.

Jump to MPEP SourceDemand for Preliminary ExaminationInterviews in National StageRequest Content and Form
Topic

PCT International Application Filing

1 rules
StatutoryRequiredAlways
[mpep-1875-01-4f78afa348dacfcc6ffa9aa4]
Invitation for Unity Required Within 7 Days
Note:
Examiner must submit a written invitation to the TC for review and mailing within 7 days of charging an international application.

If a written invitation is required, the examiner should, if possible, submit that written invitation to the TC for review and mailing within 7 days from the date the international application is charged to the examiner.

Jump to MPEP SourcePCT International Application FilingPatent Cooperation Treaty
Topic

Statement Under Article 19

1 rules
MPEP GuidanceRequiredAlways
[mpep-1875-01-f453466565ca2a01fe9873da]
Examiner Must Explain Lack of Unity
Note:
The examiner must provide reasons why an international application does not meet the unity of invention requirement and specify claim groups that could comply.

The “Invitation to restrict or pay additional fees,” Form PCT/IPEA/405, is used to invite the applicant, at his/her option, to restrict the claims to comply with the requirements of unity of invention or to pay additional examination fees. In addition, the examiner must explain the reasons why the international application is not considered to comply with the requirement of unity of invention. The examiner must also specify, on Form PCT/IPEA/405, at least one group or groups of claims which, if elected, would comply with the requirement for unity of invention.

Jump to MPEP SourceStatement Under Article 19Interviews in National StageUnity of Invention Standard

Citations

Primary topicCitation
Article 19 Amendment Scope
Article 34 Amendments
37 CFR § 1.475
MPEP § 1850
Request Content and FormPCT Rule 68.2

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