Round Lot Redefinition: Stock Market's Snooze Button Moment
Published Date: 12/10/2025
Notice
Summary
NYSE Arca is updating its rules to match a new official definition of a 'round lot'—which is basically a standard group of shares for trading. This change affects traders and brokers using the exchange and takes effect right away, with no extra costs involved. It keeps things clear and consistent for everyone buying and selling stocks.
Analyzed Economic Effects
1 provisions identified: 1 benefits, 0 costs, 0 mixed.
Round Lot Sizes Aligned with Reg NMS
NYSE Arca changed its rule so the definition of a “round lot” matches Regulation NMS. Under that rule (implemented the first business day of November 2025), a round lot is: 100 shares for stocks with average closing price $250.00 or less; 40 shares for $250.01–$1,000.00; 10 shares for $1,000.01–$10,000.00; and 1 share for $10,000.01 or more. This update (filed November 25, 2025) affects traders, brokers, and investors using the exchange by changing how orders are classified as round lots, odd lots, or mixed lots.
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