Cboe sets out how EDGX will trade overnight as US exchanges target 6 December for 23/5

Cboe EDGX Exchange will be the only one of Cboe’s four US equities exchanges to trade overnight when US exchange trading moves to roughly 23 hours a day, five days a week. The design is set out in Cboe’s EDGX Equities Overnight Trading FAQ, which the exchange says is current as of 23 September 2026, and in a Trade Desk rollout notice. BZX, BYX and EDGA will keep their existing hours. For the wider timetable across exchanges, SIPs and clearing, see our 23-hour trading overview.

The regulatory basis

The SEC gave accelerated approval to the change on 29 May 2026, in Release No. 34-105587 (File No. SR-CboeEDGX-2026-019, as amended by Amendment No. 1). EDGX filed the proposal on 31 March and replaced it in full with Amendment No. 1 on 26 May. The SEC’s notice of the original filing (Release No. 34-105206) appeared in the Federal Register on 15 April 2026 (91 FR 20213), and the approval order on 3 June 2026 (91 FR 33238). According to the order, the rules let EDGX offer trading in equity securities and exchange-traded products 23 hours a day, five days a week.

Approval is not the last step. Under the approved rules, EDGX will not start the session until the consolidated-data plans can collect and disseminate quotes and trades at all times overnight. Before going live, EDGX must still file a further rule change confirming that it can meet its Exchange Act obligations overnight and that the plans are ready. Only then will it announce the implementation and go-live dates by exchange notice. If that filing is not made within 18 months of approval, the exchange must propose removing the overnight rules. As of 27 October, no such confirming filing appeared on Cboe’s EDGX rule-filings page.

Hours and sessions

From launch, EDGX’s sessions will be (FAQ, Q8–Q9; all times ET):

• Order acceptance (queueing): 8:55pm – 9:00pm, Sunday to Thursday evenings
• Overnight Trading Session: 9:00pm – 4:00am
• Pre-Market: 4:00am – 9:30am, up from the current 8:00am start
• Regular Trading Hours: 9:30am – 4:00pm
• Post-Market: 4:00pm – 8:00pm

The new session replaces EDGX’s current 4:00am–8:00am Early Trading Session. The trading week will run from 9:00pm on Sunday to 8:00pm on Friday. From Monday to Thursday, Cboe will restart the system at about 8:05pm and expects it to be back by 8:25pm. On Sundays, startup begins at about 1:35pm to allow longer connectivity testing. For UK readers: once US clocks go back on 1 November, 9:00pm ET is 02:00 GMT and the 8:00pm ET close is 01:00 GMT.

All NMS securities will be eligible. Cboe says there will be no opening auction at 9:00pm: orders queued from 8:55pm are released to the book in order of arrival. Trades executed between 9:00pm and midnight take the next calendar day’s trade date. Overnight prints carry the existing “T” sale condition and count towards consolidated volume.

Order types, clearing and fees

The FAQ says market orders and unpriced pegged orders will not be accepted overnight. All other order types permitted today in the Early Trading and Pre-Market sessions remain available. The rollout notice adds that pegged orders without a cap price will also not be permitted in the Pre-Market and Post-Market sessions. EDGX then clarified its rulebook in SR-CboeEDGX-2026-071 (Release No. 34-106683). It was filed on 13 October for immediate effectiveness, published by the SEC on 16 October and will become operative alongside the 23x5 rules. The new rule text states: “Orders without a limit price will not be eligible for execution outside of Regular Trading Hours.” The filing also provides that a Day order entered overnight, or during order queueing, expires at the end of Regular Trading Hours on the business day to which that overnight session belongs. No FIX or BOEv3 protocol changes are planned. Existing Early Trading Session time-in-force values carry over, and a new “Hold Early Orders Until” port attribute replaces the “Early Trading Session Opt-Out” and “Hold Early to 7am” settings, which Cboe will retire on trade date 7 December.

Self-clearing members’ MPIDs will be enabled for the session automatically unless the firm notifies the exchange otherwise in writing. Non-clearing members must submit an EDGX Overnight Trading Session Clearing Letter of Guarantee, signed by their clearing firm, for the MPIDs they want enabled, with a separate letter for each clearing relationship they intend to use overnight. Until Membership Services has approved and activated it, they cannot trade overnight. The requirement for a separate overnight guarantee was written into Rule 11.13(a) by SR-CboeEDGX-2026-061 (Release No. 34-106412).

Asked whether EDGX expects to set different transaction charges for the session, the FAQ answers: “Not at this time.” EDGX’s approved filing says any effect on its fee schedule will be addressed in a subsequent fee filing. EDGX will route to other exchanges, and to off-exchange venues in Cboe’s Dark Routing Technique (DRT) programme, to the extent they are open overnight. No new connectivity or dedicated ports are needed, and there will be no specific market-maker obligations overnight.

Market data and the midnight boundary

Cboe will add a Time Reference message to its BZX and EDGX multicast and TCP PITCH, TOP and Last Sale feeds, and the FAQ adds the Auction feed. The message is sent at each restart and whenever the clock passes midnight ET. On the Summary Depth and Cboe One feeds, timestamps change from nanoseconds past midnight to nanoseconds past epoch. Cboe says the change is needed because, in aggregated feeds, time can cross midnight, go back and cross it again within one session. The rollout notice puts these market-data changes, and the new restart times, into production from trade date 2 November, ahead of the trading-hours change.

Prerequisites and testing

Cboe lists four milestones that must be met before launch: SEC approval, real-time DTCC trade processing across the whole session, SIP readiness, and primary listing markets publishing corporate-action information before 9:00pm (FAQ Q6, Q29). EDGX intends to trade all production symbols from the first night the SIPs go live, which Cboe says is targeted for 9:00pm on Sunday 6 December (trade date 7 December). From trade date 9 November it plans a parallel production period in which the test symbols ZBZX and ZTST can be traded overnight in production.

On the SIP side, the SEC approved the CTA/CQ and UTP plan amendments on 26 June 2026. They allow the processors to run from 9:00pm ET on Sunday to 8:00pm ET on Friday, with a one-hour pause from 8:00pm ET Monday to Thursday, and record the operating committees’ statement that implementation will occur on 6 December 2026. The UTP SIP’s Vendor Alert 2026-20, dated 6 July, lists the remaining industry test dates as 30 October (an intraday fallback test), 6 November, 20 November and 4 December (a confidence test). Each test runs from 11:00pm ET on Friday to midday on Saturday, over production multicast channels.

Other rule work for 23/5 is also in place. The SEC approved temporary overnight Limit Up-Limit Down price bands on 5 August (Release No. 34-106042, 91 FR 51515). On 7 October it put into effect, on a temporary basis of up to 120 days, an amendment moving the time at which the Consolidated Price used for overnight price bands is calculated from 7:45pm to 7:30pm ET (Release No. 34-106624). EDGX has also filed to keep the 4:00am resumption time after a Level 3 market-wide circuit-breaker halt (SR-CboeEDGX-2026-062). For securities that BZX lists, BZX has filed a mandatory corporate-action halt framework under Rule 11.29 (91 FR 58507). It names eight categories, including symbol and CUSIP changes, splits and mergers, and adds a ninth, catch-all category for other events where the exchange decides a halt is needed. As proposed, the halt is applied before 9:00pm ET on the evening before the action takes effect, and trading resumes through an 8:00am halt auction.

The competitive field

Cboe’s FAQ names 24X, Nasdaq, NYSE Arca and MEMX as the other exchanges that have announced plans to trade between 9:00pm and 4:00am. The SEC’s EDGX order relies on earlier approvals for 24X (exchange registration, Release No. 34-101777), NYSE Arca (SR-NYSEArca-2024-89, Release No. 34-102400) and Nasdaq (SR-Nasdaq-2025-109, Release No. 34-105199). Nasdaq’s 23/5 hub describes a 9:00pm–4:00am session that, together with its existing extended hours, will form a “Global Trading Session”. It says the industry’s move is “currently expected to occur on Sunday, December 6, 2026, pending SIP readiness as well as any applicable SEC rule changes”. Nasdaq Texas and PSX keep their current hours. Our earlier report covers the clearing, risk-control and LULD filings from other venues.

What firms need to check

• Desks: Liquidity will be split across several exchanges overnight, and EDGX will not run an opening auction. With orders lacking a limit price barred outside Regular Trading Hours, overnight flow on EDGX will be limit orders, so price protection and order-type logic need checking. A Day order entered at 9:00pm will stay eligible until the 4:00pm close of the same trade date, which affects order lifetimes and risk limits.
• Brokers: Non-clearing members need a signed overnight letter of guarantee, approved by Cboe, before the first night, and clearing firms must decide which clients to guarantee overnight. Extended-hours risk disclosures to customers and the next-day trade-date convention for trades before midnight both feed through to confirmations, allocations, and books and records.
• Venues and vendors: Feed handlers must process the Time Reference message and the switch to epoch-based timestamps from 2 November. The nightly restart resets sequence numbers on every port and feed. Cboe advises members to prepare for variable restart times and to rehearse the restart in certification. The test symbols from 9 November and the remaining SIP test dates are the last chances to test before production.
• Timing risk: 6 December is a target, not a certainty. It depends on DTCC, the SIPs and EDGX’s confirming rule filing, so firms should plan for the possibility that the date moves.