What institutional investors should know about after-hours trading for U.S. equities

U.S. equities are moving toward near-continuous trading, but institutions should use overnight access selectively because liquidity, spreads and execution costs will vary sharply by time and venue.

• Starting December 6, 2026, Nasdaq and NYSE Arca are expected to expand trading to up to 23 hours a day, five days a week, with a daily pause from 8 p.m. to 9 p.m. ET.
• The Securities Information Processor will extend its operating hours, while changes to clearing infrastructure are intended to support a 23.5-hour weekday market; weekend trading will still face settlement constraints.
• Russell Investments' 1H 2026 Global Trading Report found that market depth and execution windows changed during policy uncertainty, the Iran conflict and events such as the SpaceX IPO.
• Overnight activity remains limited: in August 2026, it accounted for 0.9% of NMS share volume and 0.8% of dollar volume on an average trade date.
• Opening and closing auctions should remain important liquidity and reference-price points, while overnight liquidity may be dispersed across exchanges and alternative trading systems, making connectivity and routing important.
• Institutions should compare the higher expected cost of trading in thinner markets with the portfolio risk of waiting for the core session, while confirming provider access, best-execution processes and overnight trading authority.

Takeaway: Most investors may keep the core U.S. session as their main execution window, but should establish rules, provider coverage and authorization procedures for event-driven trades when waiting would leave the portfolio materially exposed.