CONSOLIDATED TAPE SYSTEM: Reg NMS Round Lots Enhancements:

The Securities and Exchange Commission (SEC) is adopting amendments to certain rules of Regulation National Market System (Regulation NMS). As part of these amendments, 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 Tier designations. Each NMS stock will be assigned a round lot size based on the average closing price on the primary listing exchange, updated semiannually, with new round lot value beginning first business day in May and November each year.

Additionally, the new rule requires the Securities Information Processors (SIPs; SIAC and UTP SIP) to represent quotation sizes in consolidated information in terms of the number of 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.

Activation will take place on Monday, November 3, 2025.

What does it really mean to our customers?

Alpaca will display the CTA/UTP (US stock) quote sizes in shares, instead of round lots, starting November 3, 2025.

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