4.2.2.1.3 Places that cannot be the First Symbol

Also in this Chapter:

• 4.2.2.1.1 Application of Indexing Codes/2000 Series
• 4.2.2.1.2 Classifying in Residual Places

In a few IPC and CPC subclasses, the Notes include the following classification rule: “The classification symbols of this subclass are not listed first when assigned to patent documents”.

As of April 2025, the rule is applicable to the following IPC subclasses: A01P, A61P, A61Q, B33Y, B82Y, and G16Y as well as the following CPC subclasses: A01P, A61P, A61Q, B33Y, B82Y, C12Y, and G16Y.

These subclasses provide a classification place for a different aspect of a subject matter, which is usually covered elsewhere in the IPC or CPC. In this way, these subclasses enable a comprehensive search of the relevant subject matter by combination of classification symbol(s) of these subclasses with symbol(s) from other subclasses.

When this rule is present, it is important that:

• symbols from these subclasses must be accompanied by an Invention-information symbol(s) from a different subclass

• in IPC or CPC classification RIO tasks, the ‘First symbol’ star should not be selected for symbols from these subclasses

As common practice, the Notes section should be checked every time an application is classified.