Must a claim be identified to a correct category of subject matter?
It is not necessary to identify a single category into which a claim falls, so long as it is clear that the claim falls into at least one category. It is also not necessary to identify a “correct” category into which the claim falls, because although in many instances it is clear within which category a claimed invention falls, a claim may satisfy the requirements of more than one category.
The answer to this question can be found in chapter 2100 of the MPEP. This chapter covers patentability.
The answer is from the 9th Edition, Revision 08.2017. Depending on future changes to the MPEP, the question and answer may or may not be applicable in later Editions or revisions.
This question and answer comes from section 2106.03 of the MPEP. The following is a brief summary of section 2106.03.
2106.03 Eligibility Step 1: The Four Categories of Statutory Subject Matter
The four categories of statutory subject matter are; processes, machines, manufactures, and compositions of matter. This section covers each of the categories along with details on how to determine whether a claim fits in a statutory category.