Used primarily in business emails and formal documents to refer to the subject line or title. Often seen in phrases like 掲題の件 (regarding the subject matter).
Regarding the subject matter, please check.
I changed the email subject to 'Regarding the meeting schedule'.
Compound of 掲 (to put up, to post) and 題 (topic, title). The exact historical derivation is uncertain, but the combination naturally yields the meaning 'posted topic' or 'subject heading'.