The SEC has begun discussing a potential expansion of US stock-market trading to 24 hours, convening a roundtable as it also indicated measures permitting trading in tokenized securities. SEC Chair Paul S. Atkins said tokenization could provide real-time securities inventory management, improving operational efficiency, reducing settlement failures and mitigating risks associated with naked short selling. The agency's consideration of longer hours follows infrastructure preparations including DTCC's 23x5 trade-capture system, overnight price bands and risk-control requirements for trading venues. Market participants have raised concerns that extended sessions can bring wider spreads, fragmented liquidity and more difficult market surveillance. The effort builds on plans for 23-hour weekday trading from Dec. 6, although overnight trading currently represents less than 1% of NMS stock volume and is concentrated in relatively few stocks.