Self-Regulatory Organizations; Proposed Rule Changes: Miami International Securities Exchange, LLC

Self-Regulatory Organizations; Miami International Securities Exchange, LLC; Notice of Filing and Immediate Effectiveness of a Proposed Rule Change To Amend Exchange Rule 515A, MIAX Price Improvement Mechanism ("PRIME") and PRIME Solicitation Mechanism

Pursuant to Section 19(b)(1) of the Securities Exchange Act of 1934 (the "Act"), ⁽¹⁾ and Rule 19b-4 thereunder, ⁽²⁾ notice is hereby given that on September 30, 2026, Miami International Securities Exchange, LLC ("MIAX" or "Exchange") filed with the Securities and Exchange Commission ("Commission") the proposed rule change as described in Items I and II below, which Items have been prepared by the Exchange. The Commission is publishing this notice to solicit comments on the proposed rule change from interested persons.

I. Self-Regulatory Organization's Statement of the Terms of Substance of the Proposed Rule Change

The Exchange proposes to amend Exchange Rule 515A, MIAX Price Improvement Mechanism ("PRIME") and PRIME Solicitation Mechanism, related to Request for Response ("RFR") messages.

The text of the proposed rule change is available on the Exchange's website at https://www.miaxglobal.com/markets/us-options/all-options-exchanges/rule-filings and at MIAX's principal office.

II. Self-Regulatory Organization's Statement of the Purpose of, and Statutory Basis for, the Proposed Rule Change

In its filing with the Commission, the Exchange included statements concerning the purpose of and basis for the proposed rule change and discussed any comments it received on the proposed rule change. The text of these statements may be examined at the places specified in Item IV below. The Exchange has prepared summaries, set forth in sections A, B, and C below, of the most significant aspects of such statements.

A. Self-Regulatory Organization's Statement of the Purpose of, and Statutory Basis for, the Proposed Rule Change

1. Purpose

The Exchange proposes to amend Exchange Rule 515A related to PRIME functionality. PRIME is a process by which a Member  ⁽³⁾ may electronically submit for execution ("Auction") an order it represents as agent ("Agency Order") against principal interest, and/or an Agency Order against solicited interest. ⁽⁴⁾ A Member (the "Initiating Member") may initiate an Auction provided all of the following are met: (i) the Agency Order is in a class designated as eligible for PRIME as determined by the Exchange and within the designated Auction order eligibility size parameters as such size parameters are determined by the Exchange; (ii) the Initiating Member must stop the entire Agency Order as principal or with a solicited order at the better of the NBBO  ⁽⁵⁾ or the Agency Order's limit price (if the order is a limit order); and (iii) with respect to Agency Orders that have a size of less than 50 contracts, if at the time of receipt of the Agency Order, the NBBO has a bid/ask differential of $0.01, the System  ⁽⁶⁾ will reject the Agency Order. ⁽⁷⁾ Members may use PRIME to execute complex orders at a net price. "cPRIME" is the process by which a Member may electronically submit a "cPRIME Order" (as defined in Rule 518(b)(7)) it represents as agent (a "cPRIME Agency Order") against principal or solicited interest for execution (a "cPRIME Auction"), subject to the criteria enumerated in Policy .12 of Rule 515A. ⁽⁸⁾

Specifically, the Exchange proposes to amend Exchange Rule 515A(a)(2)(i)(D)  ⁽⁹⁾ related to Request for Response ("RFR") messages for PRIME and cPRIME Auctions. Currently, the System will reject RFR responses submitted with a price that is not equal to or better than the initiating price. The Exchange now proposes to process these messages and to provide a cancellation message at the conclusion of the Auction.

The Exchange notes that at least one other options exchange with a price improvement auction does not reject auction responses prior to the completion of the auction. ⁽¹⁰⁾

2. Statutory Basis

The Exchange believes that the proposed rule change is consistent with Section 6(b) of the Act, ⁽¹¹⁾ in general, and furthers the objectives of Section 6(b)(5) of the Act, ⁽¹²⁾ in particular, in that it is designed to prevent fraudulent and manipulative acts and practices, to promote just and equitable principles of trade, to foster cooperation and coordination with persons engaged in regulating, clearing, settling, processing information with respect to, and facilitating transactions in securities, to remove impediments to and perfect the mechanism of a free and open market and a national market system, and, in general, to protect investors and the public interest. The Exchange also believes the proposed rule change is consistent with the Section 6(b)(5)  ⁽¹³⁾ requirement that the rules of an exchange not be designed to permit unfair discrimination between customers, issuers, brokers, or dealers.

The Exchange's proposal to not reject responses that are inferior to the initiating price is consistent with the Act because it will encourage responders to submit more aggressive prices resulting in greater price improvement. The proposed amendment protects investors and the public interest by introducing competitive uncertainty to the auction process to drive meaningful price improvement and prevent responders from anchoring to the initiating price. The Exchange believes that including all auction responses ( i.e., not rejecting auction responses that are inferior to the initiating price) protects the integrity of the auction and will encourage aggressively priced responses to be submitted. Auction responses priced inferior to the initiating price that could not participate in the Auction will be cancelled at the conclusion of the Auction.

B. Self-Regulatory Organization's Statement on Burden on Competition

The Exchange does not believe that the proposed rule change will impose any burden on competition that is not necessary or appropriate in furtherance of the purposes of the Act.

The proposed change will not impose any burden on intramarket competition because all market participants that submit auction response messages will be treated in a similar fashion.

The Exchange does not believe the proposed rule change will impose any burden on intermarket competition that is not necessary or appropriate in furtherance of the purposes of the Act because it relates to orders submitted into the PRIME or cPRIME Auction mechanism on the Exchange. Additionally, the Exchange notes that the rules of at least one other options exchange with a price improvement auction does not reject inferior priced responses until the completion of the auction. ⁽¹⁴⁾

For all the reasons stated, the Exchange does not believe that the proposed rule change will impose any burden on competition not necessary or appropriate in furtherance of the purposes of the Act, and believes the proposed rule change will enhance competition.

C. Self-Regulatory Organization's Statement on Comments on the Proposed Rule Change Received From Members, Participants, or Others

Written comments were neither solicited nor received.

III. Date of Effectiveness of the Proposed Rule Change and Timing for Commission Action

Because the foregoing proposed rule change does not: (i) significantly affect the protection of investors or the public interest; (ii) impose any significant burden on competition; and (iii) become operative for 30 days after the date of the filing, or such shorter time as the Commission may designate, it has become effective pursuant to Section 19(b)(3)(A)(iii) of the Act  ⁽¹⁵⁾ and subparagraph (f)(6) of Rule 19b-4 thereunder. ⁽¹⁶⁾

A proposed rule change filed under Rule 19b-4(f)(6)  ⁽¹⁷⁾ normally does not become operative prior to 30 days after the date of the filing. However, Rule 19b-4(f)(6)(iii)  ⁽¹⁸⁾ permits the Commission to designate a shorter time if such action is consistent with the protection of investors and the public interest. The Exchange has asked the Commission to waive the 30-day operative delay so that the proposal may become operative immediately upon filing. The Exchange states that its proposal to amend its PRIME and cPRIME functionality to include all auction responses ( i.e., not reject inferior priced auction responses) in the Auction and cancel responses that could not participate in the Auction at the conclusion of the Auction is similar to at least one other options exchange with a price improvement auction. ⁽¹⁹⁾ The Exchange believes states that permitting the Exchange to immediately implement its proposal will improve execution quality by enhancing the auction process to the benefit of market participants by eliciting the best possible prices through competitive responses. For these reasons, and because the proposed rule change raises no new or novel legal or regulatory issues, the Commission finds that waiver of the 30-day operative delay is consistent with the protection of investors and the public interest. Accordingly, the Commission waives the 30-day operative delay and designates the proposed rule change to be operative upon filing. ⁽²⁰⁾

At any time within 60 days of the filing of such proposed rule change, the Commission summarily may temporarily suspend such rule change if it appears to the Commission that such action is necessary or appropriate in the public interest, for the protection of investors, or otherwise in furtherance of the purposes of the Act. If the Commission takes such action, the Commission shall institute proceedings under Section 19(b)(2)(B)  ⁽²¹⁾ of the Act to determine whether the proposed rule change should be approved or disapproved.

IV. Solicitation of Comments

Interested persons are invited to submit written data, views and arguments concerning the foregoing, including whether the proposed rule change is consistent with the Act. Comments may be submitted by any of the following methods:

Electronic Comments

• Use the Commission's internet comment form ( https://www.sec.gov/rules/sro.shtml ); or

• Send an email to [email protected]. Please include file number SR-MIAX-2026-41 on the subject line.

Paper Comments

• Send paper comments in triplicate to Secretary, Securities and Exchange Commission, 100 F Street NE, Washington, DC 20549-1090.

All submissions should refer to file number SR-MIAX-2026-41. This file number should be included on the subject line if email is used. To help the Commission process and review your comments more efficiently, please use only one method. The Commission will post all comments on the Commission's internet website ( https://www.sec.gov/rules/sro.shtml ). Copies of the filing will be available for inspection and copying at the principal office of the Exchange. Do not include personal identifiable information in submissions; you should submit only information that you wish to make available publicly. We may redact in part or withhold entirely from publication submitted material that is obscene or subject to copyright protection. All submissions should refer to file number SR-MIAX-2026-41 and should be submitted on or before November 6, 2026.

⁽¹⁾  15 U.S.C. 78s(b)(1).

⁽²⁾  17 CFR 240.19b-4.

⁽³⁾  The term "Member" means an individual or organization approved to exercise the trading rights associated with a Trading Permit. Members are deemed "members" under the Exchange Act. See Exchange Rule 100.

⁽⁴⁾ See Exchange Rule 515A(a).

⁽⁵⁾  The term "NBBO" means the national best bid or offer as calculated by the Exchange based on market information received by the Exchange from OPRA. See Exchange Rule 100. The term "OPRA" means the Options Price Reporting Authority, LLC. See Exchange Rule 100.

⁽⁶⁾  The term "System" means the automated trading system used by the Exchange for the trading of securities. See Exchange Rule 100.

⁽⁷⁾ See Exchange Rule 515A(a)(1).

⁽⁸⁾ See Exchange Rule 515A.12(a).

⁽⁹⁾  Members may submit responses to the RFR (specifying prices and sizes). RFR responses shall be an Auction or Cancel ("AOC") order or an AOC eQuote. The System will reject RFR responses submitted with a price that is not equal to or better than the initiating price. See Exchange Rule 515A(a)(2)(i)(D).

⁽¹⁰⁾ See Nasdaq Phlx Rule Options 3, Section 13(b)(1)(I).

⁽¹¹⁾  15 U.S.C. 78f(b).

⁽¹²⁾  15 U.S.C. 78f(b)(5).

⁽¹³⁾ Id.

⁽¹⁴⁾ See supra note 10.

⁽¹⁵⁾  15 U.S.C. 78s(b)(3)(A)(iii).

⁽¹⁶⁾  17 CFR 240.19b-4(f)(6). In addition, Rule 19b-4(f)(6) requires a self-regulatory organization to give the Commission written notice of its intent to file the proposed rule change, along with a brief description and text of the proposed rule change, at least five business days prior to the date of filing of the proposed rule change, or such shorter time as designated by the Commission. The Exchange has satisfied this requirement.

⁽¹⁷⁾ Id.

⁽¹⁸⁾  17 CFR 240.19b-4(f)(6)(iii).

⁽¹⁹⁾ See supra note 10.

⁽²⁰⁾  For purposes only of waiving the 30-day operative delay, the Commission has considered the proposed rule's impact on efficiency, competition, and capital formation. See 15 U.S.C. 78c(f).

⁽²¹⁾  15 U.S.C. 78s(b)(2)(B).

⁽²²⁾  17 CFR 200.30-3(a)(12) and (59).