Cboe BZX has filed to replace its fixed 4:00 a.m. and 7:00 a.m. pre-market start designations with an optional Start Time instruction. A member could choose, in 30-minute increments before regular trading hours, when an order entered early becomes eligible for execution. BZX filed the change on 15 October; the SEC published it on 28 October as an immediately effective, non-controversial proposal.[1][2]
The change is about eligibility timing, not an order guarantee. BZX would continue accepting orders from 2:30 a.m. Eastern Time, and an order without a Start Time would still become eligible according to its time-in-force at the Early Trading Session, Pre-Opening Session or regular session. Because BZX trading does not begin before 4:00 a.m., the earliest Start Time with practical effect would be 4:00 a.m.; the latest would be 9:00 a.m.[1][3][4]
How the flexible instruction would work
Order entry and eligibility under the proposed Start Time framework
| Situation | Proposed handling | Operational implication |
|---|---|---|
| Order entered before 4:00 a.m. without Start Time | Becomes eligible under its time-in-force at the existing session boundary | Default behavior remains available; Start Time is optionalSource 1Source 3 |
| Order entered at 5:15 a.m. with an 8:00 a.m. Start Time | Accepted but held ineligible until 8:00 a.m. | A broker can stage an order without manually releasing it at the chosen timeSource 1 |
| Several orders share the same Start Time | Handled in time sequence, beginning with the oldest timestamp | The instruction delays eligibility but does not erase time priority within that start groupSource 1 |
| Post Only, ISO, specified Market, Minimum Quantity/RHO, IOC or FOK order | Existing acceptance restrictions apply before 7:00 a.m. or, if later, before the designated Start Time | Order types considered unsuitable for queueing cannot simply be parked earlySource 1 |
| Start Time during regular trading hours | Not permitted | The instruction is a pre-market staging control, not an intraday scheduling toolSource 1 |
At each selected Start Time, eligible orders would be placed on the BZX book, routed, cancelled or executed according to their terms. That makes the instruction useful to broker routers that want to stage flow around liquidity events, anticipated news or a client-defined release time. It also creates a new control point: the broker must preserve the customer instruction, selected Start Time, original timestamp, time-in-force and any reason the order was rejected before eligibility.[1]
The acceptance restrictions deserve separate testing. BZX is not changing which five order categories are restricted; it is tying the restriction to the later of 7:00 a.m. or the selected Start Time. A system that validates only the clock time, but not the order type and intended eligibility time, could accept a staged instruction that the exchange will reject. Firms accessing both BZX and EDGX should also confirm that similar labels are mapped to the correct venue rules rather than assuming every session is identical.[1]
BZX intends to introduce Start Time on 7 December 2026 alongside EDGX. Its order-entry window and existing time-in-force choices remain in place; the new instruction controls when a staged pre-market order first becomes eligible to execute.[1]
Sources & further reading
- SR-CboeBZX-2026-086: Start Time order instruction U.S. Securities and Exchange Commission · 28 Oct 2026 · Accessed 30 Oct 2026
- Cboe BZX equities rule filings: SR-CboeBZX-2026-086 Cboe Global Markets · 15 Oct 2026 · Accessed 30 Oct 2026
- BZX Exchange Rule Book: Rule 11.1 trading hours and order entry Cboe Global Markets · Accessed 30 Oct 2026
- Cboe U.S. equities trading hours Cboe Global Markets · Accessed 30 Oct 2026