MIAX changes PRIME auction rule to process all response messages
The amendment, filed Sep. 30, 2026 (File No. SR-MIAX-2026-41), takes effect immediately and applies to MIAX members using the PRIME and cPRIME auction mechanisms.
On September 30, 2026, Miami International Securities Exchange, LLC filed a proposed rule change under Section 19(b)(1) of the Securities Exchange Act of 1934 and Rule 19b-4, identified as Release No. 34-106655; File No. SR-MIAX-2026-41. The Commission has designated the change effective immediately pursuant to Section 19(b)(3)(A)(iii) and Rule 19b-4(f)(6).
The amendment revises Exchange Rule 515A(a)(2)(i)(D) governing Request for Response (RFR) messages for PRIME and cPRIME auctions. Currently the System rejects RFR responses submitted with a price that is not equal to or better than the initiating price. The proposed language would allow the System to process such responses and issue a cancellation message at the conclusion of the auction.
The Exchange states the purpose is to encourage responders to submit more aggressive prices, thereby increasing price improvement and protecting investors. It notes that at least one other options exchange with a price-improvement auction does not reject inferior priced responses until the auction completes (Nasdaq Phlx Rule Options 3, Section 13(b)(1)(I)).
The Exchange asserts the change imposes no undue burden on competition, stating that all market participants submitting auction responses will be treated similarly and that the amendment aligns with the Act's objectives of preventing fraudulent practices and promoting a free and open market. No written comments were solicited or received.
The Commission is publishing this notice to solicit comments from interested persons.
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