Both the updated reporting requirements under EMIR (see here) and MiFID II will require transactions to be reported, using the Legal Entity Identifier (LEI) to specify the parties to a trade.
This week, ESMA issued this briefing note reminding market participants of their obligation to obtain LEIs. Under MiFIR, transaction reports made by Investment Firms must use LEIs to identify many types of party. In some cases, it is not permitted to enter into transactions with an entity unless an LEI has been obtained from them. The issue has also been reported here on the Reuters web site.
This is another piece of work that must be undertaken by firms in order to be ready for MiFIR, EMIR and other regulations.