Cboe EDGX Aligns Round Lots: Smooth Sailing for Share Standards
Published Date: 11/21/2025
Notice
Summary
Cboe EDGX Exchange is updating its rules to match a new official definition of a 'round lot'—basically, the standard number of shares in a trade. This change affects traders and brokers using the EDGX platform and takes effect immediately, with no extra costs involved. It also tweaks some related rules to keep everything smooth and clear.
Analyzed Economic Effects
2 provisions identified: 2 benefits, 0 costs, 0 mixed.
EDGX adopts new 'round lot' sizes
If you trade on the Cboe EDGX Exchange as a broker or trader, the Exchange will use the Rule 600 definition of a “Round Lot” starting November 3, 2025. That definition assigns round lot sizes by average closing price: $250.00 or less = 100 shares; $250.01–$1,000.00 = 40 shares; $1,000.01–$10,000.00 = 10 shares; and $10,000.01 or more = 1 share. The Exchange changed Rule 11.6(s)(1) to refer to the primary listing market’s Rule 600 assignment so EDGX’s rulebook matches the federal definition.
Round-lot sizes adjust twice yearly
Round lot sizes for each NMS stock will be recalculated on a semiannual schedule using a one-month Evaluation Period: trading days in March determine the round lot assigned on the first business day in May, and trading days in September determine the round lot assigned on the first business day in November. For any security that becomes an NMS stock during an operative period, a round lot will be 100 shares.
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