Revision History


Version	Date	Description
1.0.0	10/08/25	Initial version for publication.
1.0.1	11/03/25	Added AccessFee to List of Message Fields (effective 02/02/26).
1.0.2	12/30/25	Updated RiskReset value U = MPID level lockout reset to F = MPID level lockout reset Updated RoutStrategy in List of Message Fields to remove references to ROBB and ROCO. Added StepUpAmount to List of Message Fields (effective 1/30/26)
1.0.3	01/26/26	Effective 03/27/26, Cboe will begin populating the nanoseconds portion for the DateTime data type.
1.0.4	01/30/26	Added OrderRestatementReason to List of Message Fields. Updated Nasdaq BX to Nasdaq Texas. Added "Send All Local Rejects" to Port Attributes.
1.0.5	03/23/26	Updated Capacity description to NotSet (0, 0x00) for TradeCancelCorrectUSEquitiesV1and TradeCancelCorrectUSEquitiesV1Block messages. Removed Trading Sessions table from Hours of Operations and added a link to the trading hours on the Cboe website. Updated SubLiquidityIndicator, ExtExecInst, and PegDifference in List of Message Fields to indicate RPI will apply to BYX and EDGX (effective 04/10/26).
1.0.6	04/14/26	Updated MassCancelInst value F to indicate that all orders that were sent under the clearing relationship specified in ClearingFirm field. If F is specified and ClearingFirm not provided, the Mass Cancel or Purge request will be rejected in List of Message Fields. Updated MPID Filter for Purge Ports port attribute to indicate that if a purge request (with the first character of MassCancelInst =F) specifies an EFID not included in the list of configured EFIDs, the purge request will be rejected. If a purge port is configured with multiple EFIDs and a purge request is sent (with the first character of MassCancelInst = A) without any EFIDs specified, the purge will be applied only to the list of configured EFIDs. Added ContraBroker and ExDestination values for Texas Stock Exchange.
1.0.7	04/24/26	Added section for Dedicated Cores.
1.0.8	05/14/26	Added Reason Code z (session end). Clarified Modify Order and ClOrdId behavior in Modify Order Message Fields.
1.0.9	05/18/26	Updated Login Request Message Fields to indicate 0 is the only allowed value for UnitSequence, and removed sentence stating the number of the port's unit as the only UnitNumber accepted. Updated Login Request Message Example. Added footnotes to Default CrossTradeFlag (BYX only) in US Equities BOE Port Attributes. Added multiple message types to List of Message Fields. Added CancelRejectedUSEquitiesV1 under Cboe to Member in Appendix A: Example Application Messages. In Appendix B: Login Playbook, added ReplayInstruction to Recommended Login and Other Login Strategies.
1.0.10	06/30/26	Pegged orders entered without a Price (44) are only accepted during RTH (effective 12/07/26). Updated TimeInForce language for EDGX 23x5 trading (effective 12/07/26). "Early Trading Session Opt-out" and "Hold Early to 7am" port attributes will be sunset 12/07/26. Added new "Hold Early Orders Until" port attribute (effective 12/07/26).
1.0.11	07/06/26	Added that BOEv3 will exclusively use Order Restated message for any MTP activity in Differences with prior versions of BOE. Noted that all MTP related cancels will be sent using an Order Restated message with LeavesQty set to zero in Order Restated Message Fields and Order Cancelled Message Fields. Updated LastShares and LastPx description in List of Message Fields. Updated Symbol data type to Text.
1.0.12	08/04/26	Added DisplayIndicator (FIX Tag 9479) value of h = Hidden Multiple Price Slide (effective 09/04/26).
1.0.13	09/08/26	Added new TimeInForce value of P = RTP (Regular Hours and Post-Market Session) (effective 10/09/26).
1.0.14	09/23/26	Clarified "Hold Early Orders Until" port attribute is applicable to all Cboe-affiliated U.S. Equities Exchanges (effective 12/07/26).
1.0.15	10/05/26	Effective 10/09/26, the maximum open order limit on EDGX will be 600,000 per port.
1.0.16	10/15/26	Clarified TimeInForce = GTD language for Overnight Trading Session (effective 12/07/26).

New to Options?

Next Level Learning for More Advanced Investors

Revision History