Introducing

US Equities Move to 23/5 Trading on December 6, 2026

Aug 26, 2026

TL;DR: On Sunday, December 6, 2026, the SIPs will begin running 23 hours a day, five days a week. The three existing sessions will stay where they are, a new Overnight session will run 9pm to 4am ET, and the market will pause for maintenance from 8pm to 9pm ET. Trade dates will also shift to a futures style convention, so Monday's trading day will begin Sunday evening.

As the industry moves toward 23-hour trading, we're preparing support across our platform to help customers build and operate for the new market structure. More details on supported products and rollout plans will be shared in the coming months.

What's changing

Beginning December 6, the equities SIPs will operate continuously from 9pm ET Sunday through 8pm ET Friday, with a technical maintenance pause each evening between 8pm and 9pm ET.

The existing three sessions will remain as they are today, while an Overnight session will be introduced. The extended session covers NMS stocks and exchange traded products. Trading in the Overnight session is optional for input participants and listing exchanges. Every listing exchange must support the session, but none are required to participate in it.

Based on current filings, we expect Cboe EDGX, NYSE Arca, 24X National, and Nasdaq to be among the first Overnight session participants.

How we got here

The SEC approved 24X National Exchange for near continuous trading in November 2024, then approved NYSE Arca's proposal to extend trading to 22 hours a day on February 11, 2025. Nasdaq filed its own proposal at the end of December 2025, and on April 10, 2026, the SEC approved it, moving Nasdaq from 16 hours a day, five days a week, to 23.

Exchanges have long been able to match orders at any hour. What has been missing is a way to report them. Under Reg NMS, quotes and trades are reported by exchange participants through the SIPs (CTA & UTP; collectively, the consolidated tape). But the SIPs were built around a day that ends after the post-market session at 8pm ET. During the Overnight session there is no consolidated best bid and offer, no reliable reference price, and no meaningful compliance surface for best execution.

This is why the SIP Plan Amendments to support Overnight sessions are so important, and the timeline shows it: the plan participants filed them in January 2026, the SEC approved them on June 26, 2026, with December 6 locked in along the way by an April amendment, and the launch and testing calendar went public on July 7. Clearing was the other structural dependency, and it is already resolved: NSCC went live on 24/5 clearing on June 29, 2026, so an overnight trade clears and settles with the same central-counterparty guarantee as one struck at noon.

Then, on August 7, 2026, came a piece of regulatory insurance. The SEC granted 24X a temporary, conditional exemption (Release 34-106061) answering the obvious question: what happens if the SIPs miss the date? The order would let 24X run its overnight session without consolidated tape coverage, but it only takes effect on January 24, 2027, and only if the SIPs haven't launched by then. If December 6 happens on schedule, the exemption never activates.

The conditions tell you how deliberately the SEC built it. 24X would have to publish a real-time feed of its overnight quotes and trades at no cost, report those trades to the tape on a delayed basis, and hand the SEC quarterly volume data, and the whole arrangement expires as soon as the extended-hours tape goes live (or on July 2, 2027, whichever comes first). The SEC said plainly that it picked the late effective date to keep the pressure on the SIPs to hit December 6. The read-through for everyone else: the launch date now has a backstop behind it, and overnight equities trading is coming either way.

Overnight Session Expectations

Session dates will decouple from calendar dates

The market will adopt a futures style convention. The entire 9pm to 8pm ET window will be a single trading day, and trades and quotes reported between 9pm ET and midnight will count under the next calendar date for statistical purposes, including volume. Monday's trading session will begin at 9pm ET on Sunday.

A note on naming. Nasdaq's rule filing describes a "Day Session" (4:00 am – 8:00 pm) and a "Night Session" (9:00 pm – 4:00 am). Nasdaq's customer-facing materials use a different split: a Global Session from 9:00pm to 9:30am ET, a US Session from 9:30am to 4:00pm ET, and a second Global Session from 4:00pm to 8:00pm ET. 

The SIP FAQs use a third term, "Extended Early Hours," for the 9:00pm to 9:30am ET stretch. Same schedule, several vocabularies. Expect to see all of them in vendor documentation.

Overnight price bands

The regular session's open and close will remain the primary pricing benchmarks, and the official session closing price will remain the 4pm ET close. Plans have been submitted for each listing exchange to publish static LULD price bands to the SIPs for the Overnight session, though it is still subject to SEC approval.

Note the LULD Bands will be static. These bands will not be derived from a single reference price, nor will they be recalculated as the session moves. In short:

  • Each listing exchange will calculate the values and provide them to the SIPs by 8pm ET.
  • The values are based on a percentage of the 4pm ET primary listing market close and the 7:45pm ET consolidated round lot sale.
  • The SIPs publish them once, at start of session (9pm ET), using the existing LULD price band message fields.
  • They remain constant for the whole overnight session. They can be republished to correct an error, but they do not respond to overnight trading activity.
  • If no bands are provided for a symbol, or both values are zero, no band message is published. Prior day values are not carried over.

At 4am ET, the SIPs will clear the overnight bands by publishing zero price band messages. From 4am until 9:30am ET, no bands will be in effect. Both are unchanged from today: regular hours dynamic LULD resumes at 9:30am ET, and no bands apply between 4pm and 8pm ET.

So the 23-hour day has three distinct band regimes: static overnight, none in the pre-market, dynamic during regular hours, none after the close.

Overnight trades are not Last Sale eligible

Trades executed outside 9:30am to 4pm ET will continue to carry the Form T sale condition (condition 12) and are not eligible to update Last Sale values. This covers both the 9pm to 9:30am ET stretch and anything after the 4pm ET close. Like today, a trade can carry Form T alongside other sale conditions.

Overnight session trades will count toward the day's consolidated volume.

TRFs and late-reported trades

FINRA's Trade Reporting Facilities will move to the same schedule, operating from 9pm ET Sunday through 8pm ET Friday, with a one-hour pause from 8pm to 9pm ET Monday through Thursday, excluding holidays. FINRA has said it intends to amend its TRF reporting rules to align with the new session.

On the SIP side there is a defined reporting mechanism for the participating TRFs: any unreported, cancelled, or corrected trades from the prior session may be submitted via Prior Day messages starting at 9pm ET in the following Overnight session.

Short Sale Restrictions

Short sale restrictions advance through a state progression across sessions: an active SSR publishes as 'continued' at the next start of day, and a 'continued' SSR then publishes as 'deactivated'. On abbreviated schedule days, regular hours still end at 1pm ET with end of day at 5:01pm ET.

Changes we’ll keep an eye out for

Overnight LULD price bands remain subject to SEC approval. Index providers have not committed to overnight calculation, though we expect them to move to 23/5 eventually as well. Final per-exchange cutover mechanics and the revised SIP transmission schedule are still to be published ahead of the launch. Any exchanges that haven't filed to participate in the Overnight session may not be in the day-one cohort.

If the SIPs cannot make the December 6 deadline for any reason, the SEC has built in a contingency: 24X National Exchange holds exemptive relief to begin overnight trading in late January 2027 and carry the session until the SIPs catch up.

We're actively preparing support for the industry's move to 23-hour trading across our platform. As implementation plans are finalized, we'll share product-specific updates, documentation, and migration guidance.

We're excited to see this evolution of the US equity markets. We believe it will have a great impact on the industry and encourage broader participation from global market participants.

Resources

Exchange rule changes

  • SEC Release 34-101777: order approving 24X National Exchange's registration as a national securities exchange, November 27, 2024
  • SEC Release 34-102400: order approving NYSE Arca's extension to 22 hours a day (SR-NYSEARCA-2024-89), February 11, 2025
  • SEC Release 34-104563: notice of Nasdaq's proposed rule change to trade 23 hours a day (SR-NASDAQ-2025-109), filed December 29, 2025
  • SEC Release 34-105199: order approving Nasdaq's 23/5 proposal, April 10, 2026

SIP plan amendments (CTA & UTP)

Clearing

Contingency

  • SEC Release 34-106061: order granting 24X temporary, conditional exemptive relief for overnight trading, effective January 24, 2027 only if the SIPs miss December 6, August 7, 2026

Operational references

Have questions? Reach out to our dedicated support staff at support@massive.com for assistance.

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