Stock Exchange Adds Safeguard Against Wild Price Swings
Published Date: 4/24/2026
Notice
Summary
Cboe BZX Exchange is updating its rules to protect traders from getting stuck with really bad prices when the market’s best bid and offer prices are far apart. This new wide market protection kicks in right away to help keep trades fair and avoid wild price swings. Traders and investors using BZX will benefit from safer, smarter order executions starting immediately, with no extra costs involved.
Analyzed Economic Effects
4 provisions identified: 3 benefits, 0 costs, 1 mixed.
New Wide Market Protection Added
BZX adopted a new wide market protection that pauses and iteratively re-displays applicable orders when the National Best Bid and Offer (NBBO) is determined to be 'wide.' The mechanism uses a drill-through process to give market, limit, Stop (Stop-Loss), and Stop-Limit orders extra execution opportunities and price protection instead of immediately allowing executions at extreme prices.
Iterative Drill-Through Timing and Pricing Rules
When triggered, the drill-through process displays an order at a Benchmark Price and can re-price the order through consecutive iterations; each iteration length is set by the Exchange on a class-by-class basis and may not exceed three seconds. The Benchmark Price is defined as the least aggressive of (1) the NBB/NBO plus a buffer amount, (2) the last trade price if it is not worse than the NBBO side, or (3) the NBBO midpoint.
Certain Orders Excluded; Pre-Close Exception
The wide market protection will not apply to bulk messages, Intermarket Sweep Orders (ISOs), Immediate-or-Cancel (IOC) orders, and all M and N capacity orders; additionally, the Exchange will not apply the wide market protection during a predetermined time before the close of Regular Trading Hours (RTH) to allow final position exits. RTH is defined as 9:30 a.m. to 4:00 p.m. Eastern Time, and the exact pre-close interval will be determined by the Exchange.
More Execution Chance in No-Bid/No-Offer Cases
BZX amended no-bid and no-offer protections so that certain market orders that previously would have been canceled or rejected (e.g., sell market orders with NBB of zero and NBO > $0.50, or buy market orders with NBO of zero) may instead enter the BZX Book at the Benchmark Price and begin the drill-through iteration if they are subject to the wide market protection. This change is intended to increase execution opportunities instead of automatic cancellations.
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Key Dates
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