MPEP 903.07
Classifying and Cross-Referencing at Allowance

This is the Ninth Edition of the MPEP, Revision 08.2017, Last Revised in Januay 2018

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903.07    Classifying and Cross-Referencing at Allowance [R-07.2015]

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.

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.


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.