4.2.2.1.3 Places that cannot be the First Symbol

Date Published

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 October 2018, the rule is applicable to the following IPC subclasses: A01P, A61P, A61Q, B33Y, B82Y and the following CPC subclasses: A61P, B33Y, B82Y, C12Y.

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 indexing tasks, the “First IPC” symbol box in the PAMS Indexing task should not be ticked for symbols from these subclasses
  • in CPC classification tasks, these symbols should not be the first symbols assigned in the CPC classification list


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