Title XI (or the Taxation Act among Lyran civilians) or, formally, the Title XI of the Lyran Starfleet Code, was a piece of legislation that regulated the conduct of economic activities, like the collection of taxes, and payments thereof, by Lyran Starfleet members, as well as the citizenry of the Lyran Star Empire.
Goursat launched a Code 47 from the Enterprise to inform Brianna Reiss of Roshak's flurry of crimes committed under Title XI. (Star Trek: The Stoneship Files: "Post-Apocalyptic Education")
Individuals that dealt with taxation (and thus Title XI) professionally were known as fiscalists. (Star Trek: The Stoneship Files: "Tax Crunch")
Chloe Galarza and Anastasia Volzhin quarreled about Title XI as applied to real estate projects, when the former envisioned a luxury real estate project near an asteroid impact site on Vrauzon. (Star Trek: False Vacuum: "Asteroid Dusting")