Do Stock Splits and Dividends Halt Overnight Trading?

Stock splits and very large dividends will halt overnight trading; routine dividends will not. Under rules Nasdaq and NYSE Arca filed with the SEC on June 29, 2026, a stock listed there that faces a forward or reverse split, a dividend worth at least 25% of its closing price, a symbol or CUSIP change, a spin-off, a merger, or a similar event is halted before 9 p.m. ET on the evening before the change takes effect and reopens at 8 a.m. ET. The rules apply once 23-hour trading begins, which is scheduled to start on December 6, 2026, subject to the securities information processors being ready and to final exchange filings.

Which corporate actions halt overnight trading under the 23/5 rules?

The rules name nine categories. Nasdaq's filing to amend Rule 4120 (SR-NASDAQ-2026-057), published by the SEC on July 8, 2026, lists a change of trading symbol, a change of CUSIP, dividends worth at least 25% of the Nasdaq Official Closing Price, forward and reverse stock splits, de-SPAC transactions, spin-offs, security-type changes such as ADRs converting into ordinary shares, and mergers or other mandatory share exchanges. The ninth category is a catch-all for any other issuer event that the exchange decides requires a halt to keep trading fair and orderly. These halts are one piece of the wider shift described in hi2morrow's overview of what changes when US stocks trade 23 hours a day.

The first eight categories leave no room for judgment: if an event falls into one of them, Nasdaq says it will not have discretion about whether to halt. The split category is drawn widely and covers subdivisions, reclassifications, and share combinations at fixed or variable ratios, whether the split stands alone or comes bundled with another event. The dividend test counts cash, stock, or other securities measured against the closing price on the day before the ex-date. A plain company name change without an exchange of shares is excluded.

NYSE Arca filed a matching amendment to Rule 7.18-E in SR-NYSEARCA-2026-71 the same day, and the New York Stock Exchange filed its own Rule 7.18 version on September 1, 2026. All three filings took effect on filing under the SEC's immediate-effectiveness procedure and become operative only when 23/5 trading starts. As of October 2026, the exchanges' own FAQs still describe the regime as subject to regulatory approval, and Nasdaq says it will announce the implementation date in a trader alert.

When does a corporate action halt start, and when does trading resume?

The halt is declared after the evening session closes at 8 p.m. and before the overnight session opens at 9 p.m. on the day before the market effective date, which is the first day the stock trades on its new basis. Nasdaq-listed stocks reopen at 8:00 a.m. ET on the effective date through the Nasdaq Halt Cross, preceded by a five-minute display-only period in which orders can be entered and changed. According to the NYSE Group FAQ on corporate action halt rules, NYSE Arca, NYSE American, and NYSE Texas listings reopen at 8:00 a.m. with a Trading Halt Auction, while NYSE-listed stocks reopen with a Trading Halt Auction after 9:30 a.m.

An affected stock therefore misses the whole overnight session and at least the first four hours of premarket trading. The halt also follows the stock to other venues. Nasdaq's FAQ on corporate action halts says that once the primary listing market declares one, every other registered national securities exchange trading the stock must halt it too, and NYSE's FAQ says the rules cover all NMS stocks, whether or not their listing exchange trades overnight. A NYSE-listed stock in a split halt does not trade on Nasdaq's Night Session either.

The halts are announced before the session starts. Nasdaq tags them with halt code "M1." NYSE's FAQ says the listing exchanges will publish them in the consolidated tape's symbol file at 8:15 p.m. and again at 8:40 p.m., and in the start-of-day reference data at about 8:55 p.m. Reverse splits move onto the same clock. Today, they are halted at 7:50 p.m. and reopen at 9:00 a.m.; under the new rules, Nasdaq and NYSE Arca reverse-split stocks will reopen an hour earlier, at 8:00 a.m.

Why isn't the 8 p.m. pause enough to process a split?

The one-hour pause was originally pitched as the place to handle corporate actions. When the SEC approved Nasdaq's 23/5 rules on April 10, 2026, the approval order said the 8–9 p.m. pause would be used for maintenance, testing, and processing corporate actions such as mergers, stock splits, and dividends that take effect the next trading day. It also warned that certain corporate actions would likely require halts beyond the pause.

The halt filings explain what goes wrong in an hour. Today the exchange and the firms connected to it use the closed overnight hours to adjust orders, quotes, reference prices, and related instructions for the next morning. Under 23/5 trading, Nasdaq and NYSE Arca now describe the pause as primarily for systems maintenance, not for complex corporate actions, and say that trading through the change could rely on incomplete or inconsistent data, with risks of price dislocations, erroneous executions, and investor confusion. Some events also create symbols or CUSIPs that do not exist yet at 7:50 p.m., which is why the halt moves to a single slot between 8 and 9 p.m.

The consolidated tape works to the same timetable. Under the CTA Extended Trading Hours FAQ, updated September 29, 2026, listing exchanges deliver corporate action updates and adjusted closing prices in a daily file by 8:00 p.m., and the tape loads them into reference data before the next session begins.

Do ordinary cash dividends stop overnight trading?

No. A routine quarterly dividend worth far less than a quarter of the share price is not on the list, so the stock keeps trading through the night. The Nasdaq global trading hours FAQ says such corporate actions and dividends take effect when trading begins at 9 p.m., the start of the new trading day.

What changes is the timing of the ex-date. A trade executed between 9 p.m. and midnight ET carries the next calendar day's trade date, so the overnight session on the evening before the ex-dividend date already trades on the ex-date. Under FINRA Rule 11140, the ex-date for a dividend below 25% of the share price is the record date, provided it is a business day.

Suppose ABC pays a $0.40 dividend with a record date of Thursday, December 10, 2026, which is also the ex-date. A buy filled at 10 p.m. on Tuesday, December 8, has a trade date of December 9, settles on December 10, and earns the dividend. A buy filled at 10 p.m. on Wednesday, December 9, has a trade date of December 10 and does not. Large dividends are handled differently on both counts: at 25% or more of the prior closing price the stock is halted, and under the same FINRA rule the ex-date moves to the first business day after the payment date.

How does a 2-for-1 split play out overnight?

Assume ABC is a Nasdaq-listed stock with a 2-for-1 forward split whose market effective date is Wednesday, December 9, 2026. ABC closes at $120.00 on Tuesday, December 8, and a trader holds 100 shares worth $12,000.

Under today's schedule, ABC trades until 8 p.m. on Tuesday, sits idle overnight, and opens Wednesday's premarket at 4:00 a.m. on a split-adjusted basis near $60. Under the 23/5 rules, ABC trades normally through Tuesday's regular and evening sessions, and Nasdaq declares an M1 halt between 8 and 9 p.m. ABC then skips the Night Session from 9 p.m. Tuesday to 4 a.m. Wednesday, which already belongs to Wednesday's trading day, and stays halted through early premarket. Orders can be entered from 7:55 a.m., and the 8:00 a.m. Halt Cross reopens the stock with the position at 200 shares and a theoretical price near $60, so its value is still about $12,000 (200 × $60.00).

If ABC were listed on the NYSE, the halt would start at the same time, but the first trade on the new basis would come after the 9:30 a.m. open. Either way, news about ABC that breaks on Tuesday evening cannot be traded on the exchanges until the stock reopens.

What happens to your open orders around a split or large dividend?

The exchange book is already empty by the time the halt begins. Under Nasdaq's 23/5 rules, every order resting on its book at 8:00 p.m. is canceled, as explained in hi2morrow's guide to what happens to open orders during the 8 p.m. trading pause. Orders kept in your broker's system are a separate question. For splits, FINRA Rule 5330 requires covered open buy orders and sell stops to be adjusted after a forward split and pending orders to be canceled after a reverse split, and brokers add their own policies, which hi2morrow's article on what happens to GTC orders after a stock split covers in detail.

The halt changes when any surviving or re-entered order can first fill. For a Nasdaq or NYSE Arca listing, the earliest chance is the 8:00 a.m. reopening auction; for a NYSE listing, it is after 9:30 a.m. An order your broker resubmits at 9 p.m. or 4 a.m. has no market to meet until then, and the reopening price can differ from the theoretical split-adjusted level.

Alexander Styopin's professional view: the corporate action halt protects traders more than it restricts them. The mistake to avoid is treating the evening before a split, a large special dividend, or a merger close as a normal overnight session. Price discovery on the new basis is compressed into a single morning auction, often with thin liquidity, so check the corporate action calendar for every position, confirm the adjusted quantity and order status before 8 a.m., and set limits for the reopening based on the adjusted price rather than the old ticket.

Educational material only. Not investment or legal advice. Corporate action processing, order handling, and settlement rules can vary by exchange, broker, account type, and jurisdiction, and the launch schedule described here may change.

Author: Alexander Styopin, hi2morrow analyst and economist with 25 years of experience in the US stock market