ESMA has updated its Q&As on transparency topics under MiFID II to clarify when ESMA will publish the first set of data needed to implement the systematic internaliser (SI) regime and the date by which firms must comply with the SI regime for the first time.  The earliest mandatory deadline for firms to comply with the SI regime is 1 September 2018 (although MiFID II will apply from 3 January 2018). However, ESMA stresses that investment firms can opt-in to the SI regime for all financial instruments from 3 January 2018 as a means of complying, for example, with the trading obligation for shares.