A Unique Transaction Identifier (Acronym: UTI), alternatively called Unique Swap Identifier (Acronym: USI) is a globally unique identifier for individual transactions in financial markets. USIs were introduced in late 2012 in the U.S. in the context of Dodd–Frank regulation, where reporting of transactions to Trade Repositories first became mandatory. European financial market regulations followed suit, with reporting to Trade Repositories under EMIR requiring UTIs from February 2014 on. The use of the UTI is also mandatory for regulatory reporting under REMIT. Strictly speaking, the term USI is specific to the U.S. regulation, while UTI is specific to EU regulations. In practice, both terms are used interchangeable, in particular within large trading firms reporting under both regimes.