Reminder - Regulation NMS Mandated Odd Lot Changes

Reference ID: C2026041701

Applicable Cboe Exchanges: BYX Equities, BZX Equities, EDGA Equities, EDGX Equities

Overview

Effective April 27, 2026, the Securities and Exchange Commission (SEC) will adopt amendments to certain rules of the Regulation National Market System (Regulation NMS) requiring the addition of odd lot quote information to the Securities Information Processors (SIPs).

Technical Details

Beginning on the effective date, the SIPs will include odd lot quotation reporting. An odd lot quote refers to a quote for a quantity that is less than the standard trading unit (i.e., round lot size) for a symbol.

The SIPs will disseminate top-of-book odd lot quotations, including:

  • the best odd lot bid and offer priced better than the NBBO across all Participants ("BOLO"); and

  • the best odd lot bid and offer priced at or better than the NBBO from each Participant.

The change to add additional levels of odd lot depth to the SIP has been deferred until May 2028.

In support of these changes, all Cboe-affiliated U.S. Equities Exchanges will be available for testing on the below dates.

Table 1. Testing Schedule
DateDescription
Saturday, March 7, 2026Odd Lot Test #1 (Functional)
Saturday, March 14, 2026Blackout No Testing
Saturday, March 21, 2026Odd Lot Test #2 (Functional/Intraday Fallback)
Saturday, March 28, 2026Odd Lot Test #3 (Functional)
Saturday, April 4, 2026Holiday Weekend Blackout No Testing
Saturday, April 11, 2026Disaster Recovery and Market Wide Circuit Breaker Level 1/2 Breach Test (Odd Lot Code is used during this DR/MWCB test)
Saturday, April 18, 2026Odd Lot Test #4 (Functional for Participants)
Saturday, April 25, 2026Odd Lot Confidence Test
Monday, April 27, 2026Odd Lot Activation

Additional Information

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