The Study Tagging File (STF) is an xml file that should be provided with the eCTD submission of any file, or group of files belonging to a study in Modules 4 and 5.
The STF file helps identify all of the files associated with a study, information is needed on each document including the document title, subject matter (defined by the headings under which the documents are located in the table of contents), relationship to other documents (e.g., all documents for a specific study report are related to one another), revision information (i.e., new, replace, delete, append), the location of the document and information on the sequence that included the document.
STF files are mandatory in the US, they are optional in CA (node extensions can be used instead of STF files) and they should not be used in EU.
Source: Study Tagging File Specification and Related Files (ICH)
