Cboe brings EDGX's Start Time instruction for pre-market orders to BZX, BYX and EDGA from 7 Dec

Cboe Global Markets will let traders on three more of its US equities exchanges choose when a pre-market order becomes eligible to execute. Filings covered by SEC notices dated 27 and 28 Oct, two of which appeared in the Federal Register on 30 Oct and 2 Nov, add a Start Time instruction to the rules of Cboe BZX, Cboe BYX and Cboe EDGA. Each exchange will implement it on 7 Dec “in coordination with the implementation of the Start Time instruction on EDGX”.

The filings are based on EDGX Rule 11.1(a)(2). EDGX adopted the instruction with its move to 23-hour, five-day trading, which the SEC approved on 29 May (our report). All three were filed on 15 Oct as non-controversial changes and took effect on filing. The SEC can still temporarily suspend them within 60 days of filing.

How Start Time works

Users can attach a Start Time, in thirty-minute increments, to an order entered before Regular Trading Hours. The order becomes eligible to execute at that time rather than at the next session open. Start Times cannot be set during Regular Trading Hours, and the instruction is optional. Orders without one behave as they do today.

At each Start Time, the exchange handles orders carrying that Start Time in time sequence, the same treatment orders already get at a session open.

Each exchange already refuses certain orders before 7:00am ET. Under the filings, those orders will not be accepted before the later of 7:00am or their designated Start Time. The categories are unchanged: Post Only orders, Intermarket Sweep Orders, most Market Orders, Minimum Quantity orders with Regular Hours Only, and orders that are IOC or FOK. BYX’s list also includes RPI Orders.

The three exchanges compared

	BZX	BYX	EDGA
Order entry opens	2:30am	6:00am	6:00am
Early Trading Session opens	4:00am	7:00am	7:00am
Earliest practical Start Time	4:00am	7:00am	7:00am
Latest Start Time	9:00am	9:00am	9:00am

All times are Eastern. On BZX, Start Time replaces the existing 4:00am and 7:00am start options. BYX and EDGA say they are not changing their order entry windows.

Why it matters

Analysis. Under current rules, an order entered before the pre-market opens becomes eligible at the open of a fixed session. With EDGX moving to near-24-hour trading, Cboe is giving users a way to queue orders and stage when they go live, instead of releasing them all at once. Applying the same instruction across BZX, BYX, EDGA and EDGX means brokers, routers and OMS vendors face one behaviour across the group. They also need to code the restriction list, which varies slightly by exchange.

Orders becoming eligible together at each half-hour Start Time could create small clusters of liquidity at :00 and :30 in the pre-market. Firms will want to see whether that liquidity forms, and how the 7:00am threshold interacts with EDGX’s overnight session. US venues are lining up extended hours around the industry move to 23-hour trading (our report).

What we are watching

• Whether Cboe publishes technical specifications or a trade desk notice ahead of 7 Dec.
• Whether other US exchange groups adopt comparable instructions as their own extended hours go live.

Sources

• SR-CboeBZX, Release No. 34-106754: Notice of Filing and Immediate Effectiveness, Start Time order instruction, SEC, 28 Oct 2026
• Cboe BYX Exchange, Release No. 34-106744: Notice of Filing and Immediate Effectiveness, Federal Register, 30 Oct 2026 (SEC notice dated 27 Oct 2026)
• Cboe EDGA Exchange, Release No. 34-106753: Notice of Filing and Immediate Effectiveness, Federal Register, 2 Nov 2026 (SEC notice dated 28 Oct 2026)