On January 17, ISDA responded to the European Securities and Markets Authority’s (ESMA) consultation on a review of transaction data reporting under the Markets in Financial Instruments Regulation (MIFIR). In the response, ISDA highlights its support for several changes proposed by ESMA to improve transaction data reporting requirements – in particular, greater harmonization with similar regimes and improved reporting efficiency. The response also highlights some areas of concern, including the introduction of a transaction identification code (TIC), non-European Economic Area trading venue TICs and challenges with new identifiers, such as the digital token identifier and chain ID. It also raises questions about the potential move in messaging format from the extensible markup language (XML) to JSON.