SEC Keeps May Odd-Lot Rollout but Delays Full Depth-of-Book Data to 2028

The SEC has granted temporary relief on one part of its Regulation NMS market-data overhaul, preserving the first-business-day-of-May 2026 launch for top odd-lot information while delaying a deeper transparency requirement until the first business day of May 2028. The order gives the three equity SIP plans more time to build and test systems for full odd-lot depth data without pausing the broader rollout.

Under the order, SIPs still have to begin disseminating the best odd-lot information in May 2026. That includes the Best Odd-Lot Order, or BOLO, which shows the highest-priced odd-lot bid above the national best bid and the lowest-priced odd-lot offer below the national best offer. What gets postponed is the requirement to publish aggregated odd-lot interest at every price level between the protected best bid and offer.

The SEC said the plans are already handling several overlapping market-data changes, including the new round-lot definitions and fractional-share reporting upgrades. In that context, the regulator concluded that a two-year delay for full odd-lot depth would better protect investors than forcing a riskier implementation timetable.

For traders, the result is a partial transparency upgrade in 2026 rather than the full package many market-structure watchers expected.

Why it matters

Odd lots make up a large share of activity in many high-priced stocks. Getting BOLO data into the consolidated feed should improve visibility inside the spread, even if the complete picture of odd-lot liquidity remains delayed.

What to watch next

Watch the May 2026 SIP rollout for data quality and vendor adoption, then track whether the industry uses the extra time to make the 2028 depth-of-book deadline stick.