This set of recommendations contains best practices for tagging keywords and subject data using NISO JATS 1.1. It treats keywords as distinct from subjects, the former of which pertain to indexing rather than generation of an eTOC or other display-related purpose. A keyword, in JATS usage, is a subject term, key phrase, abbreviation, indexing word, taxonomic structure, or other expression that is associated with the entire article for the purpose of searching and indexing. A subject, in JATS usage, is a term describing a document’s content, or a component document’s content, for the purpose of grouping documents for display or print for the purpose of browsing. Both subjects and keywords can use uncontrolled or controlled vocabularies.