Miami International Securities Exchange files rule change to expand market maker role in PRIME auctions

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Market Makers in PRIME auctions

Highlights

MIAX filed an immediate-effect rule change with the SEC to allow assigned Market Makers as contra parties in PRIME and cPRIME auctions under Rule 515A.
Implementation is planned for Q3 2026, with a Regulatory Circular to be issued at least 30 days prior to market participants.
MIAX states the change will increase price improvement opportunities and competition in options auctions, aiming to benefit investors and the national market system.

Rule filing outlines auction access changes

Securities and Exchange Commission notice shows that MIAX has filed a proposed rule change to amend Exchange Rule 515A, which governs the MIAX Price Improvement Mechanism, or PRIME, and the PRIME Solicitation Mechanism.

Under the proposal, orders for accounts of Market Makers assigned in the relevant options class would be permitted to be solicited as a contra party to the Agency Order submitted for execution in a PRIME or cPRIME Auction. The filing takes immediate effect upon notice, while the Commission publishes it to solicit comments from interested parties.

MIAX says it plans to implement the functionality in the third quarter of 2026. The exchange also says it will issue a Regulatory Circular at least 30 days before the implementation date to notify market participants.

Competition and investor impact in options trading

MIAX says removing the current prohibition on assigned Market Makers acting as contra parties in PRIME and cPRIME auctions is intended to increase price improvement opportunities. The exchange argues that allowing assigned Market Makers to participate in that role could expose more orders to auction-based price improvement.

The exchange also says the amendment promotes competition in PRIME and cPRIME auctions, including competition to initiate those auctions. In its filing, MIAX says the change helps remove impediments to a free and open market and supports the national market system while protecting investors.

No written comments were solicited or received, according to the notice.

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