aurum lustrale
AURUM LUSTRA´LEwas a tax imposed by Constantine, according to Zosimus (2.38), upon all merchants and traders, which was payable at every lustrum, or every four years, and not at every five, as might have been expected from the original length of the lustrum. This tax was also called auri et argenti collatio or praestatio, and thus in Greek ἡ συντέλεια ἡ τοῦ χρυσαργύρου. (Cod. 11, tit. 1; Cod. Theod. 13, tit. 1; Orelli-Henzen, Inscr. 6507.) A some-what similar tax was the aurum negotiatorium, first mentioned under Caligula, which, however, went to the support of the aerarium, or public treasury, not the imperial fiscus (Suet. Cal. 40, 41). It does not appear to have been permanent, and is perhaps the same as the duty repealed by Nero on the petition of the trading classes (Tac. Ann. 13.51). In the confused narrative of the Augustan historian, it is mentioned first as imposed under Alexander Severus, then excused together with the aurum coronarium (Lampr. Al. Sev. cc. 24, 32).
[W.S] [W.W]A tax imposed by Constantine on all merchants and traders, and payable at every lustrum, or every five years. See Zosimus, ii. 38.