For decades, 4:00pm has given compliance teams a clean dividing line. Pre-clearance approvals lapse at the close, blackout periods start or finish, restricted-list updates come into force, and employees know exactly when an approval stops being valid. That certainty is about to disappear.
According to StarCompliance, from 6 December 2026, Nasdaq and NYSE plan to run a trading schedule from Sunday at 9:00pm ET through to Friday at 8:00pm, broken only by a planned one-hour maintenance window each evening. Technically the market will still close, but the pause is closer to a quick nap than a full night’s rest.
Across the Atlantic, the London Stock Exchange has signalled that LSE24 is expected to launch in the first half of 2027. The question for compliance functions is simple but uncomfortable: what does “market close” actually mean when equities can trade for 23 hours a day?
The SEC’s roundtable on 17 September examined the wider consequences of round-the-clock trading, covering overnight surveillance, clearing and settlement, investor protection, cybersecurity, staffing, systems resilience and market-data continuity.
Commissioner Hester Peirce also flagged concerns around supervision, thinner overnight order books, wider spreads and the practical difficulty of handling problems at 3:00am. For compliance teams, this is not merely an extra session bolted onto the day. It undermines assumptions baked into policies and controls designed around a clearly bounded trading day.
Overnight activity is still a small slice of the US equity market, but it is growing fast. SEC figures show overnight trading represented only 0.9% of National Market System share volume in August 2026, yet average daily overnight volume jumped 359% year on year to roughly 144.6m shares, with more than 4,200 NMS stocks trading overnight on a typical day.
The real risk is less about volume and more about whether employees can trade during windows that existing approvals and surveillance were never built to cover.
The planned schedule shows how quickly definitions blur. The Night Session will run from 9:00pm to 4:00am ET, followed by Pre-Market, Regular Market Hours and Post-Market trading until 8:00pm.
Trades executed between 9:00pm and midnight will carry the next trading day’s trade date. Imagine an employee granted approval at 10:00am, valid “until market close”. Does that mean 4:00pm or 8:00pm? Could they trade once the Night Session opens? And what happens if a blackout or restricted-list change lands between sessions?
Firms should be asking five questions. Which policies rely on terms like “market close”, “trading day” or “business day”? How long should pre-clearance approvals last, and when should restrictions apply across every session and market? Can systems correctly identify overnight activity and its trade date? Will the firm itself trade in the extended day, and how must controls adapt? And who handles exceptions outside normal compliance hours?
Compliance teams need not work 23 hours a day, but their controls must reflect a market that does. With further expansion likely, this is a structural shift rather than a one-off configuration task. The closing bell remains, but its role as a compliance boundary is fading.
StarCompliance’s full post can be viewed here.
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