Texas Stock Exchange Tweaks Auction Rules for Fairer Trades
Published Date: 4/29/2026
Notice
Summary
The Texas Stock Exchange is updating how its Opening and Closing Auctions work to make prices fairer and the process smoother. They’re changing some special late orders to follow new price limits based on recent trades, not just the best current prices. These changes affect traders using these auctions and will start soon, helping everyone trade smarter without extra costs.
Analyzed Economic Effects
4 provisions identified: 4 benefits, 0 costs, 0 mixed.
Late Auction Orders use Participation Bands
The Exchange will constrain late auction orders (renamed LOO.L and LOC.L) to a dynamic Participation Band instead of the NBBO. The Participation Band is calculated per security from quotes and/or trades over a lookback period of between 2 and 30 minutes or 20 and 500 events, and is recalculated every five seconds between 9:28–9:30 a.m. for opens and 3:58–4:00 p.m. for closes. If a late order is more aggressive than the Upper or Lower Band immediately prior to the auction, its price is adjusted to that band.
Earlier cut-off and no order modifications near auctions
The Exchange will change cut-off and modification windows: LOC and MOC orders may be submitted only until 3:58 p.m. (previously 3:59 p.m.), LOC.L orders may be submitted starting at 3:58 p.m. (previously 3:59 p.m.), Eligible Auction Orders may not be modified or cancelled after 3:58 p.m., and RHO orders cannot be modified between 9:28–9:30 a.m. These rules apply to the Opening and Closing Auctions.
New auction data published every five seconds
The Exchange will change what it publishes before auctions: it will disseminate Matched Shares and the Offset Side every five seconds from 8:00–9:28 a.m. (opens) and 3:00–3:58 p.m. (closes), and beginning at 9:28 a.m. (opens) and 3:58 p.m. (closes) it will publish the Participation Band, Lower Band Auction Interest, and Upper Band Auction Interest every five seconds. The Exchange says these data help liquidity providers assess supply/demand before the auction.
New tie-breaker step for auction pricing
The Exchange is adding an additional tie-breaker when multiple price levels tie on executed volume and total imbalance: it will choose the entered price at which shares would remain unexecuted in the auction, and if multiple prices qualify then the price closest to the Volume Based Tie Breaker is used. This applies to the TXSE Official Opening Price, Closing Price, and Auction Only Price.
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