Cboe Proposes Delaying Openings in Wild Market Starts
Published Date: 4/30/2026
Notice
Summary
The Cboe BZX Exchange wants to change how it starts trading each day by delaying the Opening Auction when the market is acting wild or uncertain. This affects traders and investors who use BZX, aiming to make opening prices fairer and more stable. The SEC is now deciding whether to approve this change, with a decision expected soon—no extra costs or delays for users yet, just smarter timing.
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Analyzed Economic Effects
4 provisions identified: 1 benefits, 1 costs, 2 mixed.
Opening Auction Can Be Delayed Up To 4m30s
The Exchange may delay the Opening Auction when the Indicative Price is outside the Collar Price Range. The process starts with a 5-second initial delay from 9:30:00–9:30:05 with checks every second, then may widen the Collar Price Range by 5% of the Volume Based Tie Breaker at 9:30:05 and again at set intervals, and the Opening Auction will occur no later than 9:34:30 a.m.
Collar Ranges Will Be Gradually Widened
If the Indicative Price remains outside the Collar Price Range, BZX will widen the Collar Price Range in the direction of the Indicative Price by a Widening Amount equal to 5% of the Volume Based Tie Breaker as of 9:30:05 a.m., with additional widenings at specified times up to 9:34:30 a.m. The system checks every second during each interval to see if the Indicative Price falls within the widened range and will open once it does or at 9:34:30 a.m. at the latest.
Official Opening Price Definition Changed
BZX proposes to define the BZX Official Opening Price as the price disseminated to the consolidated tape as the market center open (rather than the market center opening trade), allowing the Opening Price to be determined by either a round-lot or an odd-lot trade. The Exchange states this may yield fewer Limit Up–Limit Down (LULD) halts and more accurate Collar Price Ranges but also means there will be no LULD price bands until the Exchange disseminates a reference price.
Order Modification/Cancellation Rules Before Opening
Eligible Auction Orders designated for the Opening Auction may not be cancelled or modified from 9:28 a.m. until the Opening Auction concludes, except Regular Hours Only (RHO) limit orders may be modified (but not cancelled) during that time. Any RHO limit orders modified from 9:28 a.m. until the Opening Auction concludes would be treated as late-limit-on-open orders.
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