Texas Stock Exchange Updates Auction Rules for Smoother 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 late order rules and tightening when certain orders can be changed or canceled, aiming to boost market confidence. These changes could affect traders using the Exchange starting soon, with no extra fees involved.
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Late Auction Orders use Participation Bands
The Exchange will stop using the NBBO to limit Late Auction Orders (formerly LLOC/LLOO) and instead constrain them to a dynamic "Participation Band" calculated from quotes and/or trades. The Participation Band is calculated security-by-security using a lookback of between 2 and 30 minutes or 20 and 500 events, is recalculated every five seconds between 9:28–9:30 a.m. (opening) and 3:58–4:00 p.m. (closing), and Late Auction Orders cannot be amended or cancelled after entry.
More auction data published before open/close
The Exchange will disseminate Matched Shares and Offset Side every five seconds from 8:00 a.m. to 9:28 a.m. (opening) and 3:00 p.m. to 3:58 p.m. (closing); beginning at 9:28 a.m. and 3:58 p.m., it will publish the Participation Band plus Lower Band Auction Interest and Upper Band Auction Interest every five seconds. These new data points show buy/sell interest at the band boundaries to help participants decide order size and price in the final two minutes.
Earlier cutoffs and no last-minute cancels
The Exchange moves the latest submission and non-cancel window earlier: LOC and MOC orders may be submitted only until 3:58 p.m. (previously 3:59 p.m.), LOC.L orders can be submitted starting at 3:58 p.m. (previously 3:59 p.m.), and Eligible Auction Orders may not be modified or cancelled after 3:58 p.m. RHO orders cannot be modified or cancelled between 9:28 and 9:30 a.m.
New tiebreaker for auction prices
The Exchange adds a new tie-breaking step for opening and closing auctions: if multiple prices tie on volume and on minimum imbalance, the auction price will be the entered price at which shares would remain unexecuted; if more than one price meets that test, the price closest to the Volume Based Tie Breaker is used. This new step mirrors functionality used by other exchanges.
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