SI

Systematic Internalizer. A firm that executes orders from its clients against its own book or against orders from other clients. MiFID treats Systematic Internalizers in some respects in a similar manner to regulated markets and MTFs. Therefore, while not subject to non-discretionary rules in the same way as regulated markets and MTFs, they are subject to certain MiFID rules including in relation to pre-trade and post-trade transparency requirements.