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Wednesday, May 7, 2025

UTP Vendor Alert #2025 - 10
Regulation NMS Mandated Round Lot Changes

Markets Impacted:

Products Impacted:

Contact Information:

What you need to know:

  • Beginning November 3, 2025, as set forth in Securities and Exchange Commission (SEC) Final Rule Notice, the SEC has adopted new definitions for “Round Lot” information under the Market Data Infrastructure (MDI) Rules to enhance the transparency for investors and other market participants of quotes and orders in NMS stocks.

  • With this change the SEC will introduce new Round Lot rules that require the following Round Lot Tier designations:

    • Share Price Round Lot Size
    $0 - $250 100
    $250.01 - $1,000 40
    $1,000.01 - $10,000 10
    $10,000.01 - more 1

  • As defined in the rule, each NMS stock will be assigned a round lot size, semiannually, based on the NMS stock’s average closing price on the primary listing exchange during a one-month Evaluation Period. The Evaluation Period are:

    • all trading days in March for the round lot assigned on the first business day in May
    • all trading days in September for the round lot assigned on the first business day of November

    During which the average closing price of an NMS stock on the primary listing exchange shall be measured by the primary listing exchange to determine the round lot for each NMS stock.

  • The UTP SIP will use the existing Issue Symbol Directory Message (Category A – Type B) to provide data subscribers with the Round Lot Size assigned to the NMS security; this message is disseminated daily every morning.

  • Additionally, the new rule requires the Securities Information Processors (SIPs) to represent quotation sizes in consolidated information in terms of the number of actual shares, rounded down to the nearest multiple of the round lot size assigned to the security. This is a change from today where quotation sizes represent the number of round lots available at the quoted price.

What is Changing?

The SEC has introduced changes to the definition of “Round Lot” information and rules that require the following Round Lot Tier designations:

Share Price Round Lot Size
$0 - $250 100
$250.01 - $1,000 40
$1,000.01 - $10,000 10
$10,000.01 - more 1

How will the Round Lot Designations be determined?

As defined in the rule, each NMS stock will be assigned a round lot size, semiannually, based on the NMS stock’s average closing price on the primary listing exchange during a one-month Evaluation Period. The Evaluation Period are:

  • all trading days in March for the round lot assigned on the first business day in May
  • all trading days in September for the round lot assigned on the first business day of November
During which the average closing price of an NMS stock on the primary listing exchange shall be measured by the primary listing exchange to determine the round lot for each NMS stock.

How will this be Disseminated to Data Subscribers?

The UTP SIP will use the existing Issue Symbol Directory Message (Category A – Type B) to provide data subscribers with the Round Lot Size assigned to the NMS security, this message is disseminated daily every morning on the UTP Data Services.

Will this affect how Data Subscribers Display Quote Sizes?

Yes, today the quote size that the SIP receives and disseminates from the exchange participants is in “increments of a round lot”. Once this change is implemented, the new rule requires the SIPs to represent quotation sizes in consolidated information in terms of the number of actual shares, rounded down to the nearest multiple of their round lot size assigned to the security.

For example:

  • Given a security with a round lot of 100 shares, a UTP participant with 300 shares to buy / sell would submit a quotation size of 3 (3 lots of 100 shares = 300) and a quotation size of 3 would be disseminated on UQDF; starting on November 3, 2025, the UTP participant would submit a quotation size of 300 and a quotation size of 300 would be disseminated on UQDF.

  • Given a security with a round lot size of 40 shares, a UTP participant with 200 shares to buy / sell would submit a quotation size of 5 (5 lots of 40 shares = 200) and a quotation size of 5 would be disseminated on UQDF; starting on November 3, 2025, the UTP participant would submit a quotation size of 200 and a quotation size of 200 would be disseminated on UQDF.

What are the testing opportunities?

Type of Testing Scheduled Dates Description
Evening Test Transmissions Nightly beginning in Aug/Sep 2025 through production launch Each weeknight between 9:30 pm – 10:30 pm, the test data will be available on the “Test Broadcast” IP Multicast channels. No registration is required to participate in evening testing.
Saturday User Acceptance Test (UAT) Tentative schedule:
September 20, 2025;
October 11, 2025;
October 18, 2025;

November 1,2025
(confidence test)		 Participants will enter data and process this through SIP. As it is generated, the UTP SIP will disseminate the data via the UTP data feed production channels.
Tentative Production Launch November 3, 2025 UTP tentatively plans for production implementation to begin November 3, 2025.

Who should I contact for additional information?