Hi,
Im looking to see if there is any way that I can tell if we traded against a brokers Systematic Internaliser (SI). If I look for Tag 574=9 would that be correct, is there a better way or is that the FIX/MiFID way we should use?
MatchType(574) was added with EP163 (https://www.fixtrading.org/packages/ep163/) in the context of MMT Trading Mode. It is intended for trades matched by an SI, defined as follows in MMT:
Trade reporting by a Systematic Internaliser (SI), which is a firm that executes orders from its clients against its own book or against orders from other clients. Systematic Internalisers are subject to pre-trade and post-trade transparency requirements under the MiFID regulations.
However, you question seems to imply that the order is not executed on an SI platform and hence you do not know whether the broker is also running an SI or not. Is that the case? Information about a broker being an SI should not play a role unless the broker also acts as an SI for the given trade.
FIX provides a number of ways to convey SI-related information, i.e. it depends on the exact use case. For example, an order can be identified as being submitted from an SI with OrderAttributeType(2594) = 5 (SI). You can also identify an SI with an instance of the Parties component using PartyRole(452) = 63 (SI). Finally, you can label any party role, e.g. 1 = Executing firm, as also being an SI with PartySubIDType(803) = SI (76). There is more…