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903    Classification [R-08.2012]

903.01   Statutory Authority [R-08.2012]

The statutory authority for establishing and maintaining a classification system is given in the following statute, which states:

35 U.S.C. 8   Classification of patents.

The Director may revise and maintain the classification by subject matter of United States letters patent, and such other patents and printed publications as may be necessary or practicable, for the purpose of determining with readiness and accuracy the novelty of inventions for which applications for patent are filed.

903.02   Basis and Principles of Classification [R-08.2012]

Many of the principles that form the basis of classification used in the U.S. Patent and Trademark Office are set forth in the “Examiner Handbook to the U.S. Patent Classification System” which can be accessed from either the Intranet on the Classification Home Page (http://ptoweb:8081/) or the Internet on the Office of Patent Classification home page ( Any questions not covered in this handbook can be directed to the Office of Patent Classification.

903.02(a)   New and Revised Classes

The establishment of new classes or subclasses and the revision of old classes are done under the guidance of the Technology Center classification contact, as follows:

  • (A) The staff performing the reclassification develops an arrangement of documents which is satisfactory for searching;
  • (B) The definition of the new class or revised class is written or modified;
  • (C) The lines between the class and other classes are drawn up;
  • (D) The subclass definitions are established and definitions of all revised classes and subclasses are included in the classification orders; and
  • (E) The Index of the U.S. Classification System and the Classification Data System files are updated.

Notification of the new class or subclass is published in a classification order. Copies of classification orders are available online to USPTO personnel from the Classification Home Page under the heading Classification Reports. The Classification Home Page (http://ptoweb:8081/) is accessible from the desktop via the Patent Examiner’s Toolkit.

903.02(b)   Scope of a Class

In using any classification system, it is necessary to analyze the organization of the class or classes to be included in the search.

The initial analysis should determine which one or ones of the several types of subject matter (manufacture, art, apparatus, or stock material) are contained in the class being considered.

Further, relative to each type of subject matter, it is necessary to consider each of the various combinations and subcombinations set out below:

Basic Subject Matter Combined with Feature for Some Additional Purpose. The added purpose is in excess of the scope of the subject matter for the class, as defined in the class definition; e.g., adding a sifter to a stone crusher which gives the added function of separating the crushed stone.

Basic Subject Matter Combined with Perfecting Feature. Features may be added to the basic subject matter which do not change the character thereof, but do perfect it for its intended purpose; e.g., an overload release means tends to perfect a stonecrusher by providing means to stop it on overload and thus prevent ruining the machine. However, this perfecting combined feature adds nothing to the basic character of the machine.

Basic Subject Matter. The combination of features necessary and essential to the fundamental character of the subject matter treated; e.g., a stonecrusher requires a minimum number of features as essential before it can function as such.

Subcombinations Specialized to Basic Subject Matter. Each type of basic subject matter may have subcombinations specialized to use therewith; e.g., the crushing element of a stonecrusher.

Subcombinations of General Utility. Each type of basic subject matter may have subcombinations which have utility with other and different types of subject matter; e.g., the machine elements of a stonecrusher. Subcombinations of this character usually are provided for in some general class so that the examiner should determine in each instance where they are classified.

903.02(c)   Establishing Subclasses and Cross-Reference Art Collections

Any examiner having the Technology Center Director’s approval to create new subclasses should contact the supervisory patent classifier (SPC) for his or her technology before work is begun. The SPC will assist the examiner in establishing any new subclass by (A) providing appropriate instructions on how to transfer patents from an existing subclass to a new subclass, (B) determining the title and definition of the newly established subclass , and (C) assigning the numeric designation to be placed on the new subclass .

All newly created subclasses will be made official so as to be a part of the defined classification system. New classification data will be added to the Subclass Data File (SDF) and Master Classification File (MCF) as appropriate. Concurrently, all automated classification indices and systems, including the EAST and WEST search tools, will be updated to reflect the new classification changes.

903.03   Availability of Foreign Patents [R-08.2012]

Many foreign patent documents received in the Office before October 1, 1995 were placed in the shoes in the Technology Center (TCs), according to either the United States Patent Classification System (USPC) or, in relatively few instances, the International Patent Classification (IPC) system. Foreign patents received by the Office after October 1, 1995 are available on the USPTO’s automated search systems, the Foreign Patent Access System (FPAS), Internet sites, and the Scientific and Technical Information Center (STIC) collections.

If the examiner desires to update the classification of a foreign patent by changing, canceling, or adding copies, he or she should forward the patent (or bibliographic information) to his or her supervisory patent classifier with a request for the desired transaction attached.

The STIC retains copies of foreign patents (see MPEP § 901.06(a)) so that foreign patents, known by country, number, and publication date, can be inspected in STIC and so that photocopies can be ordered.

Examiners confronted with language problems in classifying foreign-language patents may call upon the Translation Branch of STIC for assistance (see MPEP § 901.06(a)).

903.04   Classifying Applications for Publication as a Patent Application Publication [R-08.2012]

Patent applications filed on or after November 29, 2000, are published as a patent application publication pursuant to 35 U.S.C. 122(b), unless certain exceptions apply. See MPEP § 1120.

Patent application publications are given a primary classification (equivalent to an original classification), and may also be given a secondary classification (equivalent to a cross reference). While there may be only one primary classification for a single patent application publication, there may be any number of secondary classifications. The selection of a primary classification of a patent application publication is based on the application’s main inventive concept using the claims as a guide. A primary classification could be any U.S. class/subclass (except cross reference art collections, digests and foreign art collection subclasses). A secondary classification is based on other inventive concepts (mandatory) or valuable disclosure (discretionary), and may be any U.S. class/subclass (including cross reference collections and digests, but excluding foreign art collection subclasses). The classification of a patent application publication is printed on the front page of the publication.

At least 9 weeks prior to the projected publication date, applications are classified using programs designed to enable entry of certain data required for publication of patent applications. Applications are classified by giving each application at least a primary classification and an international classification. The suggested international classification(s) corresponding to each assigned U.S. classification is provided. In addition, if a figure is to be published, the figure is selected at the time of classification.

903.05   Addition, Deletion, or Transfer of U.S. Patents and U.S. Patent Application Publications [R-08.2012]

Requests for addition, deletion, or transfer of official copies of U.S. patentsand U.S. patent application publications may be carried out by using the Patent Post Publication Classification Manager and the PGPub Post Publication Classification Manager, which are available online from the Classification Home Page under the heading Patents, their Classifications and Locations. The Classification Home Page is accessible from the desktop via the Patent Examiner’s Toolkit.

Using these tools, examiners can request the following transactions:

  • (A) Add any classification(s) from the U.S. Patent Classification system as a cross-reference (XR) classification to a patent or a secondary classification to a patent application publication.
  • (B) Delete XR classification(s) or secondary classification assigned to the Technology Center (TC) of the person requesting the deletion.
  • (C) Change original classifications (ORs) or primary patent application publication classification to a classification in the TC of the person requesting the change.
  • (D) Add or delete any International Patent Classification system (IPC) classification to a patent.

903.06   Harmonized Subclasses [R-08.2012]

The U.S. Patent Classification System (USPC) includes subclasses that have been harmonized with subclasses from the European Patent Office (EPO) and the Japan Patent Office (JPO). These subclasses are regularly populated with documents from the EPO and JPO databases. Subclasses that have been harmonized have a designation of “EPO,” “JPO,” or “EPO/JPO” in parentheses following the subclass title to indicate if the subclass has been harmonized with the EPO or JPO or with both systems.

903.07   Classifying and Cross-Referencing at Allowance [R-08.2012]

When an application is passed to issue, it is the duty of each primary examiner to personally review the original classification and cross-referencing made by his or her assistants in the issuing classification boxes on the Image File Wrapper (IFW) issue classification form in the Office Action Correspondence Subsystem (OACS). This form provides space for the full name of the “Primary Examiner” to show that the review has been made.

An examiner with full signatory authority who acts personally on an application and sends it to issue should stamp and sign his or her name on the IFW issue classification form ONLY in the “Primary Examiner” space. A line should be drawn through the “Assistant Examiner” space on the form, as appropriate, to make it clear that the absence of information in the box was not an oversight.

An application, properly classified at the start of examination, may be classified differently when it is ready for allowance. The allowed claims should be reviewed in order to determine the subject matter covered thereby. It is the disclosed subject matter covered by the allowed claims that determines the original and any mandatory cross-reference classification of U.S. patents.

The procedure for determining the classification of an issuing application is as follows: every claim, whether independent or dependent, must be considered separately for classification. A separate mandatory classification is required for each claim which is classifiable in a different class or subclass; some claims, particularly in chemical areas, may require plural classifications. After all mandatory classifications have been determined, the classification to be designated as the original (OR) is determined. If all mandatory classifications are in the same class, the original classification is the mandatory classification that, looking at the schedule from the top down, is the most indented subclass array in which any classifications are assigned, in certain circumstances (e.g., the genus-species array), however, modifications of this rule may apply. See the “Examiner Handbook to the U.S. Patent Classification System” for an explanation of genus-species classification.

If the mandatory classifications are in different classes, the original classification is determined by considering, in turn, the following criteria:

  • (A) selection based on the most comprehensive claim,
  • (B) selection based on priority of statutory category of invention,
  • (C) selection based on superiority of types of subject matter, and
  • (D) selection among classes in the “related subject” listing at the front of the manual of classification.

It should be noted that the criteria, supra, may be superseded by

  • (A) special circumstances, e.g., superconductor technology and biotechnology are superior to all other subject matter,
  • (B) prior placement of patents for a particular body of art, or
  • (C) particular class lines and class notes.

Once the controlling class is determined, the original classification, looking at the schedule from the top down, is the mandatory classification that is the most indented subclass of the first subclass array in which any classifications are assigned.

For a more complete discussion of this subject, see the “Examiner Handbook to Classification” which is available online to USPTO personnel from the Classification Home Page under the heading Classification Guides and Bulletins. The Classification Home Page (http://ptoweb:8081/) is accessible from the desktop via the Patent Examiner’s Toolkit.

Once the original classification is determined, all remaining mandatory classifications are designated as cross-references, as are any additional discretionary classifications that the examiner wishes to apply to the patent.

The examiner must complete the IFW issue classification form to indicate the class and subclass in which the patent should be classified as an original and also the classifications in which it should appear as a cross-reference. The examiner should be certain that all subclasses into which cross-references are placed are still valid.

All examiners must include alpha subclass designators in the issuing classification boxes on the IFW issue classification form at the time of issue when appropriate. This applies to both the original classification and the cross-reference classification. Any time that a patent is being issued in or cross-referenced to a subclass containing alpha subclasses, the alpha designation for the proper alpha subclass must be included. No other designation is permissible. Inclusion of only the numeric designation of a subclass which includes an alpha subclass designation is an incomplete and improper entry. A numeric subclass from which alpha subclasses have been created is designated with an “R” (denoting residual), and if the patent does not fit an indented alpha subclass, the “R” designation must be included. It is permissible to place multiple copies of a patent into a single set of alpha subclasses.

Digests and cross-reference art collections should also be included in the issuing classification boxes on the IFW issue classification form, but the original classification must never be a digest or cross-reference art collection. The indication for a copy of a patent in a digest or cross-reference art collection must be in the cross-reference area of the issuing classification boxes. A digest must be identified by class number, alpha characters DIG, and appropriate digest number.

U.S. patents cannot be classified in subclasses beginning with “FOR,” since these are exclusively for foreign patents. See also MPEP § 901.07.


Where an official classification order affects an application already passed to issue, the Office of Patent Classification oversees any necessary changes. Patents issuing from applications which already have been sent to the printer will be reclassified .

903.07(a)   Cross-Referencing — Keep Systematic Notes During Prosecution

Throughout the examination of an application, systematic notes should be kept as to cross-references needed either due to claimed or unclaimed disclosure. Examiners handling related subject matter should be consulted during prosecution (whether they handle larger unclaimed combinations or claimed or unclaimed, but disclosed, subcombinations), and asked if cross-references are needed.

Each consultation involving a question of the propriety of the classification of subject matter and/or the need for a cross-reference must be recorded in the SEARCH NOTES box on the file wrapper and must include: the name of each examiner consulted, the date that the consultation took place, and the results of the consultation including the consulted examiners’ or examiner’s indication of where claimed subject matter is properly classified and where subject matter disclosed but unclaimed is properly classified and whether or not a cross-reference is needed.

A cross-reference MUST be provided for all CLAIMED disclosure where possible and inserted in the issuing classification boxes at time of issue.

903.07(b)   Issuing in Another Technology Center Without Transfer

When an examiner issues a prospective patent in another Technology Center (TC), he or she notes in the space provided on the issuing classification area on the IFW issue classification form the class and subclass of the other TC, and in parentheses the number of the other TC. A concurring primary examiner from the other TC must initial the area to the right of the original classification. When the primary examiners from the two TCs disagree on the proper original classification of the allowed claims, the application should be submitted for resolution to the supervisory patent examiner (SPE) having jurisdiction over the art area to which the application is presently assigned. The SPE will work with the SPE of the other impacted area for resolution. In the case where an impasse develops, the application will be forwarded to the classification dispute TC representative panel for a final determination (see MPEP § 903.08(d)). At all stages of the process, the application is to be given a high priority.

Only when both examiners concur in the proposed classification of the patent, or where there has been a ruling by the SPE, or a final determination by the classification dispute TC representative panel, may patent applications sent to issue from one TC be assigned to classes in another TC.

903.08   Applications: Assignment and Transfer [R-08.2012]

The titles “supervisory patent examiner” and “primary examiner,” as used in this Chapter 900, include in their definition any person designated by them to act on their behalf. It is recognized that authority to accept or refuse the transfer of an application may be delegated when such authority is deserved.

The Technology Center (TC) to which an application is assigned is responsible for its examination until such time as the application is officially transferred to another TC.

The primary examiners have full authority to accept any application submitted to them that they believe is properly classifiable in a class in their art unit.

Applicants may be advised of expected application transfers by using form paragraph 5.03.

¶ 5.03    Reassignment Affecting Application Location

The Art Unit location of your application in the USPTO has changed. To aid in correlating any papers for this application, all further correspondence regarding this application should be directed to Art Unit [1].

Examiner Note:

This paragraph should be used in all Office actions when the location of an application is changed due to a reassignment of the art, transfer of the application to a different Art Unit, or transfer of an examiner and the examiner’s docket.

903.08(a)   New Applications

New nonprovisional applications are assigned to the various Technology Centers (TCs) in the first instance by the Office of Initial Patent Examination (OIPE).

The supervisory patent examiner or his/her designee reviews each application to determine whether it properly belongs in his or her art unit. If it does belong in the art unit, it is processed as a new receipt. See MPEP § 903.08(b).

When a new application is received which, in the opinion of the primary examiner, does not belong to his or her TC, he or she may request transfer of it to another TC. See MPEP § 903.08(d).

If the search in connection with the first action develops art showing proper classification elsewhere, the transfer is usually initiated before the first action is prepared and mailed.

903.08(b)   Classification and Assignment to Examiner

Every nonprovisional application, new or amended, and including the drawings, if any, when first assigned to a Technology Center (TC) must be classified and assigned to an examiner for examination. The supervisory patent examiner normally classifies the application and assigns the applicationto an examiner. Provisional applications are not classified or assigned since they are not examined.

If an examiner other than the supervisory patent examiner is given the responsibility of assigning applications, time so spent may, at the TC Director’s discretion, be charged to “Assisting SPE.”


Applications filed under the Patent Cooperation Treaty (PCT) are normally classified on the basis of the first claimed invention (i.e., Claim 1) in the application. The following special situations, however, apply:

  • (A) if a U.S. national application has been acted upon by an examiner to whom the national application was assigned on the basis of the controlling (not necessarily the first) claim, a subsequent PCT application claiming priority of the national application will normally be assigned to the same examiner, or to the examiner’s art unit in his/her absence;
  • (B) in all other situations where a U.S. national application and a corresponding PCT application are copending, irrespective of which application was filed first, every effort should be made to ensure that both applications are assigned for search and examination to the examiner to whom the PCT application would normally be assigned on the basis of the first claimed invention, or to the examiner’s art unit in his/her absence;
  • (C) if a PCT application has been the subject of international search and possibly international preliminary examination outside the U.S., a U.S. national phase application or a U.S. national application claiming benefit of the PCT application will be assigned like any other application, i.e., on the basis of the controlling claim.

The object of having the U.S. national and PCT applications assigned to the same examiner is to promote consistent search and examination results.

See MPEP § 903.08(d) for a discussion of transfer procedures.

903.08(c)   Immediate Inspection of Amendments

Upon the receipt of an amendment which makes a transfer proper, steps should be taken promptly in accordance with the transfer procedure outlined in MPEP § 903.08(d).

903.08(d)   Transfer Procedure


Each Technology Center (TC) has developed internal procedures for transferring application between art units and resolving application assignment disputes.


Where a supervisory patent examiner (SPE) believes an application (including PCT applications), either new or amended, does not belong in his or her art unit, he or she may request transfer of the application from his or her art unit (the “originating” art unit) to another art unit of a different TC (the “receiving” art unit).

Where the application is a PCT application or an application that has been docketed to an examiner, the decision as to the classification resolution and assignment of the application is made by agreement between the SPEs involved in the transfer.

Where the application is an application (other than a PCT application) that has not been docketed to an examiner, the decision as to the classification resolution and assignment of the application is made by agreement between the SPEs involved in the transfer. If no agreement can be reached between the SPEs, the application may be forwarded to the classification dispute TC representative panel of the TC where the application was originally assigned for a final decision. The classification dispute TC representative panel consists of designated representatives from each TC.

Before an application is sent to a receiving art unit of a different TC, the application must be fully reviewed to ensure that all appropriate areas in the originating TC have been considered with respect to the classification of the application. In all cases when a transfer is initiated, the application must be sent on transfer inquiry to a receiving art unit. Even if the application is confusing or contains unfamiliar subject matter, the SPE of the originating art unit must make his or her best judgment as to where the application should be classified and attempt to transfer it there.

Where an application’s claims include a combination of limitations for plural disciplines (chemical, electrical, or mechanical), an SPE or primary examiner may request transfer to another discipline, notwithstanding the fact that the controlling claims are properly classified in his or her art unit, on the ground that the application is “best examinable” in the other discipline. In this instance, the SPE or primary examiner requesting transfer should cite art showing the limitations classifiable in his or her discipline. For discussion of the situations in which assignment of an application on a “best examinable” basis may be proper, see MPEP § 903.08(e).


When the SPE or primary examiner of the originating art unit determines that a transfer is appropriate, he or she must complete the Application Transfer Request form in PALM EXPO and provide a full explanation of the reasons for classification in the receiving art unit. An eDAN message should also be sent notifying the receiving art unit of the transfer. At least one of the following should be included in the form in the space provided:

  • (A) Identification of the controlling claim examinable in another TC;
  • (B) Identification of any existing informal transfer agreement; or
  • (C) Other reasons – with full explanation.

If the SPE or examiner of the originating art unit believes an application has been improperly assigned to their art unit, but is unable to determine an appropriate place to send the application, a “gatekeeper” or search assistant should be consulted. A listing of examiners who function in this role may be found at http://ptoweb/patents/tsa/. It is noted that “gatekeepers” or search assistants exist in all of the TCs except the TC that examines design applications (TC 2900).

If the receiving SPE or primary examiner agrees to accept the application, he or she classifies and assigns the application. The transfer is effected by accepting the application in PALM EXPO.

If the receiving SPE or primary examiner refuses to accept the application, the reasons for refusal must be entered in PALM EXPO. For an image file wrapper (IFW) application, an eDAN message stating that the application is being returned should be sent to the originally assigned art unit. The refusal must be recorded in the PALM EXPO transfer inquiry page. Where the application is an application (other than a PCT application) that has not been docketed to an examiner, the originating art unit may then either accept the application for examination or send the disputed transfer application to the classification dispute TC representative panel for final resolution. The panel considers the statements and evidence of both the originating and receiving art units and assigns the application to the art unit that has jurisdiction over the art in which the controlling claims of the application are properly classified.

Under certain circumstances, the classification dispute TC representative panel, contrary to controlling classification rules, may assign an application to a class or art unit which the panel deems is better equipped to examine the application. See MPEP § 903.08(e).

Every application, no matter how peculiar or confusing, must be assigned somewhere for examination. Thus, in contesting the assignment of an application, the SPE or primary examiner should indicate another class that is a better class in which to classify the application, rather than simply arguing that the application does not fit the examiner’s class.

If an application contains both classification issues and issues unrelated to classification, e.g., a dispute both as to the classification of claims and the propriety of restriction, the issues unrelated to classification should be resolved first. If, thereafter, classification issues still need to be addressed, application transfer may be appropriate. For the procedure in the classification groups for applications which contain examining corps issues, see MPEP § 903.08(e).

The question of need for a restriction requirement does not influence the determination of transfer.

Applications filed under the Patent Cooperation Treaty and such other special applications designated by competent authority must be hand-carried throughout the transfer process unless an established practice is in place for expediting the delivery of these applications. If an application is hand-carried at any stage of the transfer process, care must be taken to update the location of the application on the PALM system each time the application is moved.

If an application has been assigned a class/subclass by the Office of Initial Patent Examination (OIPE) and the application is routed to an art unit that does not examine applications assigned to that class/subclass, an eDAN message to "OIPEClass/GAUMismatch" IFW mailbox should be sent.

903.08(e)   General Guidelines Governing the Assignment of Nonprovisional Applications for Examination

This section applies only to nonprovisional applications. It does not apply to provisional applications since such applications are not examined.

The following are only general guides, and exceptions frequently arise because of some unusual condition. Patent examiners are confronted with an already existing classification made up of newly revised classes, those revised years ago and which have somewhat outgrown their definitions and limits, and still others made a generation ago and never changed. Also, these classes are based on different theories and plans, some on art, some on structure, some on functions, some on the material worked upon, and some apparently on no theory or plan at all. The patent examiners cannot change this existing condition as each application comes up for assignment, but must seek to place the cases into this patchwork and try to get the applications where they are appropriately assigned. An application will be assigned as follows:

  • (A) The assignment of nonprovisional applications follows, as far as possible, the rules or principles governing the classification of patents. Applications are generally assigned on the basis of where the application would have an original classification, if the claims it contains were in a patent.
  • (B) The criteria by which the original classification is determined are set forth in MPEP § 903.07.
  • (C) The claims and statement of invention are generally taken as they read; however, claims must be read in light of the disclosure (claimed disclosure). Any attempt to go behind the record and decide the case upon what is deemed the “real invention” would, it is believed, introduce more errors than such action would cure. Supervisory patent examiners (SPEs) cannot possess the specific knowledge of the state of the art in all the classes that the patent examiners collectively possess. Further, such questions are matters of merit for the examiners to determine and are often open to argument and are subject for appeal.
  • (D) Within a class, looking down from the top of the schedule, the OR subclass is chosen from among the classifications of the claimed disclosure according to whichever one is the most indented subclass of the first subclass array.
  • (E) As stated in MPEP § 903.07, the location of the United States patents constituting the prior art is generally controlling over all else. (Note: Where time permits, obvious misplacements of the patents constituting the prior art are corrected, but to straighten all lines as the cases come up for assignment would require the time of several people and would often involve a reclassification of an entire class.)
  • (F) Ordinarily, an application cannot be assigned to a class which includes one element or part only of several claimed in combination. The claim is treated in its entirety.
  • (G) The classification dispute TC representative panel is authorized in all cases, where they evaluate the facts as warranting it, to assign applications for examination to the TC best able to examine the same. Since assignment for examination on this basis will at times be contrary to classification of patents containing the same character of claims, the classification dispute TC representative panel will indicate the proper classification of the patent, if such claims are allowed.

    Thus, in cases where there is a claim drawn to hybrid or mixed subject matter and the SPE in one discipline determines that the application requires consideration by, or may be best examined by, a TC in one of the other technical disciplines, chemical, electrical, or mechanical, he or she may request a transfer of the application on a “best examinable” basis, in accordance with this subsection.

    Some examples of applications which may be thus submitted include the following:

    • (1) An application containing a hybrid claim wherein, for instance, a product is defined merely in terms of the process for producing it. See MPEP § 705.01(e), situation (A).
    • (2) Where an application properly assigned to a mechanical or electrical class contains at least one claim to mixed subject matter, a part of which is chemical, the application may be assigned to the appropriate chemical art unit for examination; or where the application is properly assigned to a mechanical class and a claim therein contains electrical subject matter, the application may be assigned to the appropriate electrical art unit for examination.

    As indicated earlier, when an application which had been assigned for examination in accordance with this subsection ultimately is allowed, it will be classified according to the controlling claim. In effect, assignment for examination may be on a “best examinable” basis, but the patent will issue and be classified according to the rules of superiority in classification; thus, the search file will have a constant set of rules governing placement of patents therein.

    Where an application is being reassigned from one examining discipline to another, under the provisions of the “best examinable” practice, the person requesting the transfer is ordinarily required to cite references pertinent to the claimed features falling under the jurisdiction of the art within his or her discipline. In those cases wherein the application of the reference(s) is not evident or clear, the transferring examiner should include a brief statement explaining the relation and possible application of the reference(s) to the claim(s); in case of dispute as to the necessity of this procedure, the classification dispute TC representative panel has power to require the statement.

  • (H) See MPEP § 903.08(b) for a discussion of how to properly assign PCT international applications and U.S. national applications associated therewith.
  • (I) When an application has been taken up by an examiner for action and a requirement to restrict is found necessary, a part of the claims being directed to matter classifiable in the TC where the case is being examined, an action requiring restriction should be made without seeking a transfer of the case to another TC. The action of the applicant in reply to the requirement for restriction may result in making a transfer of the application unnecessary.
  • (J) Ordinarily, where all the claims of an application are for an article made of a specific composition or alloy with no other structure of the article recited, the application will be assigned to the composition or alloy class.
  • (K) A class of cases exists in which either no art or a divided art is found and in which no rule or principle is involved. Such cases are placed where, in the judgment of the classification TC representative panel, they will be best searched and adjudicated. It is often impossible to so explain a decision in this class of cases as to satisfy, or in any way aid, the examiners interested. Indeed, the reasons for or against sending such cases one place or another may be so evenly balanced that no reason of any value can be given.
  • (L) An examiner seeking the transfer of a case may make a search, both of his or her own class and the class to which he or she thinks the case should be transferred, and the examiner in charge of the art unit should ensure the record includes the result of the search.
  • (M) When an application is received by the classification dispute TC representative panel in which there is a matter under dispute which is not related to the classification of a claim but which is in the purview of the TCs, e.g., propriety of a restriction requirement, timeliness of submission for transfer, etc., as well as a dispute over the classification of claims, the application will be returned to the originating TC for resolution on the issues unrelated to the classification.

It is important that newly received applications be immediately screened for these situations so that, if necessary, the applications may be promptly returned to the originating TC.

If after resolution of the issues unrelated to the classification, there is still a dispute as to which TC should examine the application, the originating application may be returned to the classification dispute TC representative panel for assignment.


The flowchart below shows the routing of undocketed applications between TCs after receipt from OIPE. (For routing of undocketed applications between art units within the same TC, see MPEP § 903.08(d).) The application should be considered by the receiving art unit in the TC (TC1), which will accept the application and assign it to an examiner, or forward it to an art unit in another TC (TC2) for consideration. An art unit in TC2 will classify and assign the application to an examiner, return the application to the SPE of the originating art unit, or forward it to an art unit in another TC (TC3). If the art unit in TC2 is not aware of any other likely classification, the application may be returned directly to the SPE of the originating art unit in TC1. In any of these scenarios, the decisions concerning the transfer must be recorded in PALM EXPO and in the case of an image file wrapper (IFW) application, eDAN messaging should also be used.

Where the application is forwarded to an art unit in TC3 and the art unit in TC3 declines to accept the application, the application should be returned to the SPE of the originating art unit in TC1.

If an art unit in TC2 or TC3 declines to accept the application and the application is returned to the SPE of the originating art unit in TC1, the SPE of the art unit in TC1 may forward the application to a classification dispute TC representative panel for resolution. The SPE of the art unit in TC1 may contact a TC classification panel representative within his or her TC. The application will be given to the TC classification panel representative and the representative will contact either the TC2 or TC3 representative (forming a classification dispute TC representative panel) to set up a conference. The classification dispute TC representative panel will evaluate any evidence presented by the disputing TCs, and make a decision on the proper classification and assignment of the application. The decision of the classification dispute TC representative panel will be final and binding.

Inter-TC Classification Dispute Resolution Procedures


SPEs and examiners must use the EXPO Transfer Inquiry function, which creates a record of the transfer inquiry history of each application and facilitates tracking of applications.

PALM EXPO will provide a routing sheet to be included in the application file when a transfer inquiry is created.

903.09   International Classification of Patents for Inventions [R-08.2012]

In accordance with the Strasbourg Agreement Concerning the International Patent Classification, the United States is required to indicate on its issuing documents the classification symbols of the International Patent Classification 2006 (Eighth Edition), hereinafter referred to as “Int. Cl..”

The complete Int. Cl. symbols must be placed in the indicated space on the Image File Wrapper (IFW) issue classification form when an application is issued.


The layout of the Int.Cl. is explained below with reference to the sample page.

A.   Section

The Classification represents the whole body of knowledge which may be regarded as proper to the field of patents for invention, divided into eight sections.

  • (A) Section Symbol — Each section is designated by one of the capital letters A through H.
  • (B) Section Title — The section title is to be considered as a very broad indication of the contents of the section. The eight sections are entitled as follows:

    A. Human Necessities

    B. Performing Operations; Transporting

    C. Chemistry; Metallurgy

    D. Textiles; Paper

    E. Fixed Constructions

    F. Mechanical Engineering; Lighting; Heating; Weapons; Blasting

    G. Physics

    H. Electricity

  • (C) Contents of Section — Each section title is followed by a summary of the titles of its main subdivisions.
  • (D) Subsection — Within sections, informative headings form subsections, which are titles without classification symbols.

Example: Agriculture

B.   Class

Each section is subdivided into classes.

  • (A) Class Symbol — Each class symbol consists of the section symbol followed by a two-digit number.

Example: A 01

  • (B) Class Title — The class title gives an indication of the content of the class.

Example: A 01 Agriculture; Forestry; Animal Husbandry; Hunting; Trapping; Fishing

C.   Subclass

Each class comprises one or more subclasses.

  • (A) Subclass Symbol — Each subclass symbol consists of the class symbol followed by a capital letter.

Example: A 01 B

  • (B) Subclass Title — The subclass title indicates as precisely as possible the content of the subclass.

Example: A 01 B Soil Working in Agriculture or Forestry; Parts, Details, or Accessories of Agricultural Machines or Implements, in General

  • (C) Subclass Index — Some subclasses have an index which is merely an informative summary giving a broad survey of the content of the subclass.

D.   Group

Each subclass is broken down into subdivisions referred to as “groups,” which are either main groups or subgroups.

  • (A) Group Symbol — Each group symbol consists of the subclass symbol followed by two numbers separated by an oblique stroke.
  • (B) Main Group Symbol — Each main group symbol consists of the subclass symbol followed by a one- to three-digit number, the oblique stroke, and the number 00.

Example: A 01 B 1/00

  • (C) Main Group Title — The main group title defines a field of subject matter considered to be useful in searching for inventions.

Example: A 01 B 1/00 Hand tools

  • (D) Subgroup Symbol — Subgroups form subdivisions under the main groups. Each subgroup symbol consists of the subclass symbol followed by the one- to three-digit number of its main group, the oblique stroke, and a number of at least two digits other than 00.

Example: A 01 B 1/02

Any third or fourth digit after the oblique stroke is to be read as a decimal subdivision of the second or third digit, respectively; e.g. 3/426 is to be read as “three slash forty-two point six”, not three slash four hundred and twenty six and is to be found after 3/42 and before 3/43, and 5/1185 is to be read as “five slash eleven point eight five,” and is to be found after 5/118 and before 5/119.

  • (E) Subgroup Title — The subgroup title defines a field of subject matter within the scope of its main group considered to be useful in searching for inventions. The title is preceded by one or more dots indicating the hierarchical position of the subgroup, i.e., indicating that each subgroup forms a subdivision of the nearest group above it having one dot less. The subgroup title is often a complete expression, in which case it begins with a capital letter. A subgroup title begins with a lower case letter if it reads as a continuation of the title of the next higher, less-indented group, i.e., having one dot less. In all cases, the subgroup title must be read as being dependent upon, and restricted by, the title of the group under which it is indented.


A 01 B 1/00 1/24 Hand tools for treating meadows or lawns (The title of 1/24 is to be read as: Hand tools for treating meadows or lawns.)
A 01 B 1/00 1/16 Hand tools Tools for uprooting weeds (The title of 1/16 is a complete expression, but owing to its hierarchical position, the tools for uprooting weeds are restricted to hand tools.)

E.   Complete Classification Symbol

A complete classification symbol comprises the combined symbols representing the section, class, subclass, and main group or subgroup.

Example showing section, class, subclass, main group and subgroup according to International Patent Classification (IPC)

  Guide Headings

The main groups in each subclass are arranged in a sequence intended to assist the user. It has not, however, been found practicable to standardize the sequence. Where several successive main groups relate to common subject matter, it is usual to provide before the first of such main groups a “guide heading” which is underlined, indicating this subject matter (see, for example, the guide heading “Ploughs” before group A 01 B 3/00). The series of groups covered by such a heading extends to the next guide heading or to a line in heavy type extending across the column, which is used when the following group or groups relate to different subject matter for which no guide heading is provided. (See, for example, the line after A 01 B 75/00.)


A.   Selecting Subclasses Corresponding to U.S. Classes

The effective scope of a subclass is defined by the following, taken together:

  • (A) The subclass title which describes, as precisely as is possible in a small number of words, the main characteristic of a portion of the whole body of knowledge covered by the Classification, this portion being the field of the subclass to which all its groups relate;
  • (B) Any references which follow the subclass title or the hierarchically higher class title. These references often indicate certain parts of the field described by the title which are covered by other subclasses and are, therefore, excluded. These parts may constitute a substantial part of the field described by the title and, thus, the references are in some respects as important as the title itself. For example, in subclass A 47 D — FURNITURE SPECIALLY ADAPTED FOR CHILDREN — a considerable part, namely school benches or desks, of the subject matter covered by the title is excluded in view of a reference to particular groups of subclass A 47 B, thus considerably altering the scope of subclass A 47 D;
  • (C) Any references which appear in groups or guide headings of a subclass and which refer subject matter to another class or subclass may also affect the scope of the subclass in question. For example, in subclass B 43 K — INSTRUMENTS FOR WRITING; DRAWING-PENS — writing points for indicating or recording apparatus are referred out of group 1/00 to group 15/16 of subclass G 01 D, thereby reducing the scope of the subject matter covered by the title of subclass B 43 K;
  • (D) Any notes or definitions appearing under the subclass title or its class, subsection, or section title. Such notes or definitions may define terms or expressions used in the title, or elsewhere, or clarify the relation between the subclass and other places. Examples are
    • (1) Note (1) appearing under the title of the subsection “ENGINES OR PUMPS,” embracing classes F 01 to F 04, which notes define the terms used throughout the subsection,
    • (2) the notes appearing under the title of subclass F 01 B, which define its scope in relation to subclasses F 01 C to F 01 P, and
    • (3) the note following the title of section C which defines groups of elements.

B.   Selecting Main Groups Corresponding to U.S. Mainline Subclasses

The scope of a main group is to be interpreted only within the effective scope of its subclass (as indicated above). Subject to this, the effective scope of a main group is determined by its title as modified by any relevant references or notes associated with the main group or with any guide heading covering it. For example, a group for “bearings” in a subclass whose title is limited to a particular apparatus must be read as covering only features of bearings peculiar to that apparatus, e.g., the arrangement of bearings in the apparatus. Guide headings are intended to be only informative and, as a rule, do not modify the scope of the groups covered by them, except where it is, otherwise, clear from the context. By contrast, references in the guide headings modify the scope of the associated groups.

C.   Selecting Subgroups Corresponding to U.S. Indented Subclasses

The scope of a subgroup is likewise to be interpreted only within the effective scope of its main group and of any subgroup under which it is indented. Subject to this, the scope of a subgroup is determined by its title as modified by any relevant references or notes associated therewith.

See volume 9 of the International Patent Classification, entitled “Guide, Survey of Classes and Summary of Main Groups” for detailed procedures for classifying into and searching Int. Cl..

Sample page from Int. Cl. 7 (7th edition, 1999) Vol. 10


The Office of Patent Classification has prepared a revised Concordance between the U.S. classes and subclasses and the Int. Cl.. In many areas, the two systems are conceptually different. With this in mind, it will be seen that a complete one-to-one correspondence between the two systems cannot be attained. An indication in the Concordance may refer to only one relevant group and not necessarily the only group in which the patent can or should be classified. For some inventions, the Concordance may not indicate any truly relevant group. Accordingly, the Concordance must be recognized as a guide to be used in conjunction with the Int. Cl., and not as a translation list.

The Concordance is updated monthly, and is available to USPTO personnel online from the Classification Home Page under the heading Search Classification Data. The Classification Home Page (http://ptoweb:8081/) is accessible from the desktop via the Patent Examiner’s Toolkit.

The Concordance may be incomplete or contain errors in some areas. Therefore, if corrections need to be made in the Concordance, members of the examining corps are requested to e-mail suggested changes to the Technology Center classification contact via their supervisory patent examiner.

903.09(a)   Locarno Classification Designations

U.S. design patents prepared for issue after June 30, 1996 include a Locarno International Classification designation as part of the bibliographic data. The purpose of the international design classification designation is to enhance accessibility of design patents in foreign design search files as well as commercial databases.

The Locarno International Classification system was developed by members of the Paris Convention for the Protection of Industrial Property and is administered by the International Bureau of the World Intellectual Property Office (WIPO).

A Locarno International Classification designation consists of two pairs of numbers separated by a hyphen. The first pair of numbers designates a design class; the second pair of numbers indicates a particular subclass within the design class. The Locarno Classification manual, available from WIPO, delineates the individual classes and subclasses and includes: (1) a general list of classes of industrial designs divided into broad subclasses; and (2) an alphabetical list of specific industrial designs with an indication of the classes and subclasses into which they should be classified.

The Locarno designation included with design patent bibliographic data indicates the original classification of the patented design only. There is no provision for cross-reference designations within the Locarno system.

Locarno International Classifications are periodically revised by the Committee of Experts of the World Intellectual Property Organization.

The Image File Wrapper (IFW) issue classification form includes an area with the heading “International Classification”. A Locarno International Classification designation must be included on the issue slip when a design application is prepared for issue. The Locarno designation is printed on the design patent preceded by INID code [51] in compliance with ST.9 of the International Bureau. The abbreviation “LOC (7) CL.” follows INID code [51] and complies with the recommended abbreviation by the International Bureau.

An example Locarno designation as it appears on a U.S. Design Patent is as follows:

[51] LOC (7) CL. 02-02

The Office of Patent Classification has prepared a Concordance between the U.S. Design Classification classes and subclasses and the Locarno International Classification. In many areas of design subject matter, the U.S. Design Classification and Locarno Classification systems are parallel. In others, the two systems are conceptually different. For example, there is no specific provision within the Locarno system for designs which are simulative of other objects. The International Classification is generally based on the nature of the design rather than ornamental appearance. Accordingly, a one-to-one relationship between the two classification systems is not always possible.

Each suggested designation in the Concordance refers to a single Locarno International class and subclass. This designation, however, is not necessarily the only pertinent class and subclass in which the design could be properly classified since for some U.S. Design Classification designations, there is no direct parallel within the Locarno system.



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Last Modified: 03/27/2014 10:10:36