The anticipated implementation of 23x5 exchange trading by December 6, 2026 represents the most significant expansion of trading hours for US national securities exchanges in decades. The SEC and the industry have been working to address the many moving regulatory and operational parts to achieve this goal. In recognition of the complexity of this trading evolution, on September 17, 2026, the SEC hosted a roundtable to discuss “moving towards 24-hour trading in the US equity markets, including preparations to support overnight trading, operations and resiliency in a 24-hour market, and opportunities and challenges for expansion.”1 The participants in the roundtable, including SEC Commissioners and staff as well as representatives from the exchanges, FINRA, DTCC, broker-dealers, issuers and industry associations, discussed the regulatory, operational and practical steps needed to accomplish this expansion in exchange trading hours.
A. Expanded Exchange Trading Hours
In response to growing investor demand in overnight trading, particularly from retail and non-US investors, trading venues are working to increase trading access around the clock. Four alternative trading systems—Blue Ocean ATS, Bruce ATS, IBKR Eos ATS and MOON ATS—currently trade in the overnight hours. An analysis by SEC staff regarding overnight trading found that the current trading volume in the overnight session is small (approximately 0.9% of total NMS share volume on an average trade date) but growing quickly (359% year-over-year).2 Accordingly, the US national securities exchanges are now looking to expand equities trading into the overnight hours.
The exchanges currently support three trading sessions from Monday through Friday: 4:00 am to 9:30 am ET, 9:30 am to 4:00 pm ET, and 4:00 pm to 8:00 pm ET. With the 23x5 trading expansion, certain exchanges would add an overnight session from Sunday through Thursday from 8:00 pm to 4:00 am ET, with a mandatory one-hour trading pause Monday through Thursday evening between 8:00 pm and 9:00 pm ET.
During the roundtable, the Commissioners and the Director of Trading and Markets indicated support for the enhanced trading opportunities. For example, Chairman Atkins noted that, beyond fulfilling investor needs, extending exchange hours could produce many other positive changes, including (1) aligning US exchange trading hours with those of overseas trading venues; (2) attracting more global capital to the US; (3) allowing investors to react more quickly to events, thereby reducing risk that accumulates overnight and increasing market efficiency; and (4) avoiding price discovery distortions from trading pauses. Chairman Atkins noted, however, that such significant changes must balance market access with investor protections.3 The following efforts by market participants to implement 23x5 exchange trading seek to maintain that balance.
B. Implementation of 23x5 Exchange Trading
The implementation of 23x5 exchange trading has been and continues to be an extensive and coordinated effort across market participants and regulators. The following highlights many of the important steps taken, or currently in progress, to expand exchange trading opportunities for investors.
1. Exchange Trading Approvals
To date, the SEC has provided conditional approval for five national securities exchanges —24X,4 Cboe EDGX,5 MEMX,6 Nasdaq,7 and NYSE Arca8—to provide 23x5 trading, allowing market participants to trade equities 23 hours a day, five days a week, by adding an overnight session to their existing trading hours. Trading during extended hours on exchanges has not yet commenced, however, because the SEC’s approvals of the 23x5 proposals were conditioned on, among other things, the readiness of the Equity Data Plans9 for consolidated market data (“SIPs”) to receive and disseminate exchange quotes and trades in the overnight hours in the same way as they do for current trading hours. Exchange representatives participating in the roundtable indicated that the exchanges planning to commence overnight trading remain on track to implement such trading when the SIPs are ready on December 6, 2026.
2. SIPs: CTA, CQ and UTP Plans
On June 26, 2026, the SEC approved amendments to the national market system plans to allow the SIPs to extend their operating hours to 9:00 pm ET Sunday through 8:00 pm ET Friday (excluding holidays), with a one-hour pause at 8:00 pm ET on Monday through Thursday for technical refreshes for the SIPs.10 The approval orders set forth December 6, 2026 as the SIPs’ launch date for 23x5 trading.11 Since the approval orders, the SIPs have continued to indicate that December 6, 2026 will be the commencement date for the expanded hours and have provided additional guidance regarding the implementation of 23x5 trading.12 Moreover, exchange representatives confirmed the December 6, 2026 date during the roundtable.
3. Clearance and Settlement
Another important market consideration for 23x5 trading is the clearance and settlement of overnight activity. Accordingly, NSCC, the central counterparty and provider of clearance and settlement services for the trading of equity securities in the US, sought and received SEC approval for extending its clearing hours to 24x5 availability, from Sundays at 8:00 pm ET to Fridays at 8:00 pm ET, supporting overnight trading activity from exchanges and alternative trading systems.13 On June 29, 2026, NSCC announced that it was live for extended trading hours.14
4. Corporate Action Information
Under the current market structure, the listing exchange for an issuer processes corporate action-related changes and updates for listed securities during the overnight hours, when the exchanges are closed to trading. Other market participants, including broker-dealers, likewise use that overnight period to process corporate action-related information and adjust quotes, orders, and related instructions. With the introduction of 23x5 exchange trading, however, there will only be a one-hour trading pause between 8:00 pm and 9:00 pm ET, which may not be sufficient for the processing of complex corporate actions across exchange and market participant systems. To address this issue, the primary listing markets have adopted harmonized rules for mandatory regulatory halts for securities subject to certain corporate actions.15 These rules seek to provide exchanges and market participants with adequate time to process complex corporate actions and make the necessary adjustments to systems, orders, quotes and reference data. It is expected that these rules will become operative in conjunction with the commencement of 23x5 trading.
Under these new rules for corporate actions, if a security is affected by any of the nine corporate actions enumerated in the proposal, the listing exchanges would implement a mandatory halt in the affected security during the period between 8:00 pm ET and 9:00 pm ET on the day immediately preceding the market effective date of the applicable corporate action or issuer-related event. The primary listing exchanges will disseminate the corporate action trading halt via the SIPs. The security would remain halted through the overnight trading session. The primary listing markets would reopen securities subject to mandatory trading halts at 8:00 am ET. If the primary listing market declares a corporate action-related regulatory halt, all other registered national securities exchanges trading in the affected security would be required to halt trading in that security as well.
The following nine categories of corporate actions are subject to a mandatory corporate action halt: (1) changes in trading symbol; (2) changes in CUSIP number; (3) large dividends; (4) stock splits (including forward and reverse splits); (5) de-SPAC transactions; (6) spin-off transactions; (7) security type change (e.g., preferred to common); (8) mergers and similar mandatory exchanges of shares; and (9) any other corporate action or issuer-related event where the primary listing market determines that a regulatory halt is appropriate for the maintenance of fair and orderly markets, the protection of investors or otherwise in the public interest.
5. FINRA’s Trade Reporting Facilities
In alignment with the expected extension of the operating hours for the SIPs, FINRA’s Trade Reporting Facilities (“TRFs”),16 which provide FINRA members with a mechanism for reporting over-the-counter trades in NMS Stocks, will extend their operating hours. Currently, FINRA’s TRFs operate from 4:00 am ET to 8:00 pm ET, Monday through Friday, excluding holidays. Beginning December 6, 2026, FINRA’s TRFs will operate from 9:00 pm ET Sunday through 8:00 pm ET Friday, with a one-hour technical pause between 8:00 pm ET and 9:00 pm ET, Monday through Thursday, excluding holidays.17 As described in its rule filing to implement these changes, the expanded hours would enable real-time public dissemination of trade reports for over-the-counter transactions in NMS Stocks executed during the overnight hours when the SIPs are operating.18
6. CAT Reporting
Efforts are also underway to facilitate CAT reporting of overnight trading on the exchanges pursuant to the CAT NMS Plan. CAT published a CAT Alert to address the CAT reporting changes that affect Industry Members with respect to 23x5 trading.19 As described in the CAT Alert, although there will be no changes to existing CAT reporting deadlines for submissions and corrections, the Industry Member definition of Trade Date has been revised to accommodate 23x5 trading. Currently, the term Trade Date is defined for Industry Members as “beginning immediately after 23:59:59.999999 ET on Trade Date T - 1 and up to 23:59:59.999999 ET of the next Trade Date T.” Effective December 6, 2026, Trade Date for Industry Members will be redefined as “the period beginning at 8:00 p.m. Eastern Time on the calendar day immediately preceding Regular Trading Hours and ending at 8:00 p.m. Eastern Time on the same calendar day as Regular Trading Hours. Regular Trading Hours shall have the meaning specified in Rule 600 of Regulation NMS of the Act for ‘regular trading hours.’”20 The CAT Alert further notes that, although trading on some US equity exchanges will begin on Sunday evening, weekends and holidays will still not be considered a Trade Date, and an event occurring on a weekend or holiday will still be assigned to the next Trade Date. Correspondingly, CAT has updated the Participant Technical Specifications to address 23x5 trading, including updating the definition for Trade Date.21
C. Investor Protection Related to 23x5 Trading
Regulators and market participants also have been considering issues related to investor protection during 23x5 trading. The regulatory approaches aim to balance allowing the expansion of trading opportunities while addressing potential issues related to trading during periods that have historically been characterized by lower liquidity, wider spreads, and the potential for increased price volatility.
1. Limit Up Limit Down Plan - Overnight Price Bands
On August 5, 2026, the Commission approved an amendment to the Plan to Address Extraordinary Market Volatility (“LULD Plan”) to address expanded trading hours.22 The LULD Plan provides a market-wide limit up limit down (“LULD”) mechanism intended to address extraordinary market volatility in NMS Stocks. The amendment establishes static price bands that will be in effect during the overnight hours (that is, from 9:00 pm ET on Sunday through Thursday until 4:00 am ET on the next calendar day) (“Overnight Price Bands”).23 The use of Overnight Price Bands are expected to commence on December 6, 2026.24
The primary listing exchange for each NMS Stock will calculate and disseminate to the SIPs an Overnight Lower Price Band and an Overnight Upper Price Band to be applied during overnight hours. The Overnight Price Bands will be based on two reference prices, as adjusted for any relevant corporate actions: (i) the official closing price of a stock as reported by the listing market for such NMS Stock; and (ii) the consolidated last round lot sale as of 7:45 pm ET. The Overnight Lower Price Band will be set 20% lower than the lower of the reference prices, and the Overnight Upper Price Band will be set 20% greater than the greater of the reference prices, subject to additional minimum band sizes and other requirements.25 Unlike the dynamically updated LULD price bands for regular trading hours, the Overnight Price Bands will remain constant throughout the overnight session. The 20% parameter used to calculate each of the two Overnight Price Bands is intended to align with the 20% parameter currently employed by ATSs for overnight trading.26
The amendment to the LULD Plan also requires that all trading centers in NMS Stocks that are operative overnight, including both those operated by the LULD Plan participants and those operated by members of such participants, establish, maintain, and enforce written policies and procedures that are reasonably designed to prevent both trades and the display of prices outside the Overnight Price Bands during the overnight hours.
The LULD Plan amendment does not require automatic trading pauses during the overnight hours if an Overnight Price Band is hit. The primary listing exchanges of an NMS Stock, however, may declare a regulatory halt when warranted to maintain a fair and orderly market, in accordance with its rules, including when orders are consistently being placed outside the bands or the price bands are otherwise limiting price discovery. The primary listing exchange will notify the SIPs if it declares a regulatory halt. Any NMS Stock subject to a regulatory halt during the overnight hours will not reopen during the overnight hours.27
The LULD Plan amendment states that the Overnight Price Bands are a first step to addressing the expansion of exchange trading to the overnight hours. The participants in the LULD Plan stated that they intend to gather and analyze information concerning overnight trading that they will then use to develop recommendations for a final proposal to address exchange trading in the overnight session.28
2. Extended Hours Trading Risk Disclosures
The exchanges and FINRA require their members to provide their customers with certain enhanced disclosures regarding the risks of trading in the overnight hours. For example, exchange rules require disclosure that trading overnight involves material trading risks, including the possibility of lower liquidity, higher volatility, changing prices, unlinked markets, an exaggerated effect from news announcements, and wider spreads, as well as risks related to trading during hours in which primary listing markets may not be open, risks of trading during hours in which there may be limited or different regulatory protections, risks of trading because of limited trading alternatives, risks related to continuous trading, and risks of trading because of the novel nature of overnight trading on exchanges.29
Similarly, FINRA requires that firms that permit customers to engage in extended hours trading provide customers with a risk disclosure statement.30 In addition, if the firm permits customers to engage in extended hours trading online, or open accounts online in which the customer may engage in extended hours trading, the firm must post a risk disclosure statement on the firm’s website in a clear and conspicuous manner. The risk disclosure must address, at a minimum, the six specific risks enumerated in FINRA Rule 2265, including the risks of lower liquidity, higher volatility, changing prices, unlinked markets, news announcements, and wider spreads, and firms must also consider whether to develop and include additional disclosures as necessary to address product-specific or other particular needs.
3. Clearly Erroneous Rules
The exchanges that plan to implement 23x5 trading have indicated that they propose to rely on their clearly erroneous rules during the overnight trading sessions.31 These exchanges determined to apply the same substantive standards and procedures currently applicable to the trading sessions other than the 9:30 am ET to 4:00 pm ET trading hours to the overnight session.
4. Use of Limit Orders
The five exchanges planning to commence trading in the overnight session plan to only allow orders with a limit price during that session.32 By requiring market participants to set the prices at which they are willing to trade during overnight sessions, the exchanges seek to limit the potential risks that may be present in the overnight hours, such as the potential for lower liquidity and wider spreads, risks that would be more acute with respect to the handling of market orders.
5. Market Wide Circuit Breakers
The exchanges and FINRA also have been considering the operation of their market wide circuit breaker rules in light of the impending expansion of exchange trading hours. These rules provide for trading halts in all US cash equity and equity options markets during a severe market decline, as measured by a single-day decline in the S&P 500 Index during regular trading hours. Currently, the triggers are set at three circuit breaker thresholds: 7% (Level 1), 13% (Level 2), and 20% (Level 3). Under the current rule, if a Level 3 Market Decline occurs at any time during the trading day, trading in all stocks will halt for the remainder of the trading day. Currently, that means that the earliest any exchange would reopen trading after a Level 3 Market Decline is 4:00 am ET the following day, because no SROs are open for trading before 4:00 am ET. After discussions among the US equity exchanges, FINRA and industry representatives, it was determined that maintaining this resumption time would be appropriate when 23x5 trading commences. Accordingly, the exchanges and FINRA are in the process of filing rule changes to amend the market wide circuit breaker rules to preserve the current resumption time after a Level 3 Market Decline—that is, trading will not resume until 4:00 am ET on the following day.33
6. Best Execution
Commissioner Peirce, in her opening remarks, raised the issue of how broker-dealers would satisfy their best execution obligation during the overnight hours, particularly given the retail investor interest in trading during the extended hours.34 A broker-dealer’s best execution obligations apply to all transactions for or with customers, regardless of the time when an order is received or a transaction is executed.35 Accordingly, broker-dealers that participate in overnight trading must comply with best execution obligations during those hours. To date, FINRA has not proposed revisions to its best execution rule in light of the proposed expansion of overnight trading to exchanges. FINRA, however, has requested comment on what additional guidance regarding best execution obligations for extended hours trading may assist firms in navigating those obligations in this evolving landscape.36 FINRA reiterated its request for comments on this issue during the roundtable.
7. Supervisory and Other Staffing Obligations
As the roundtable participants discussed, all market participants need to consider the staffing needs, including any applicable licensing requirements for such staff, for the extended hours. Roundtable participants noted that such staffing would need to cover the surveillance, market access controls, compliance oversight, technology, cybersecurity and other regulatory and operational processes during the new trading hours. Broker-dealers that participate in overnight trading also must ensure they meet their supervisory obligations for the overnight activity.37 During the roundtable, FINRA indicated that it continues to analyze supervisory and other regulatory obligations related to extended trading hours as a part of its rule modernization initiative.38
D. Issuer Considerations
During the roundtable, Commissioners and the Director of Trading and Markets emphasized the need for issuers, like investors, to prepare for substantial changes to the markets with the expansion of trading hours. For example, in his introductory remarks, Chairman Atkins encouraged issuers to provide feedback on how expanded trading hours may affect their execution of certain corporate actions, their obligations to disseminate material information to the market, and the obligation to make SEC filings during EDGAR filing hours. Commissioner Peirce echoed these comments, noting that issuers currently make filings and publicize material information prior to or after core trading hours. She questioned whether the move to 23x5 trading would require issuers to change their behavior.39
E. Possible Future Expansion to 24x7 Trading on Exchanges
In his remarks at the roundtable, the Director of Trading and Markets noted the possibility for a future expansion to 24x7 trading on exchanges. The final panel of the roundtable took the opportunity to look beyond 23x5 trading to around-the-clock trading. Although the current focus is on 23x5 trading and no concrete proposals are currently on the table for 24x7 trading, market participants are considering this potential next step and the infrastructure and other changes required to support it.
