HORIZON KINETICS ASSET MANAGEMENT LLC - 19 May 2026 Form 4 Insider Report for MIAMI INTERNATIONAL HOLDINGS, INC. (MIAX)

Reporting relationship: 10%+ Owner
Issuer ticker: MIAX
Reported as of: 19 May 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 21 May 2026, 17:21:22 UTC
Prior SEC filing: 19 May 2026
Next SEC filing: 21 May 2026
Source filing: View source filing
Reporting owner signature: /s/ Jay Kesslen, attorney-in-fact

Key filing fact

HORIZON KINETICS ASSET MANAGEMENT LLC filed Form 4 for MIAMI INTERNATIONAL HOLDINGS, INC. (MIAX) on 21 May 2026.

Key facts

This page summarizes HORIZON KINETICS ASSET MANAGEMENT LLC's Form 4 filing for MIAMI INTERNATIONAL HOLDINGS, INC. (MIAX).
1 reported transaction and 0 derivative rows are listed below.
Accepted by SEC: 21 May 2026, 17:21.

Change

Previous filing in this sequence was filed on 19 May 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001056823 Primary reporting owner

HORIZON KINETICS ASSET MANAGEMENT LLC

Relationship: 10%+ Owner
Address: 470 PARK AVE S, 8TH FLOOR SOUTH, NEW YORK
Signature: /s/ Jay Kesslen, attorney-in-fact
Signature date: 21 May 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

MIAX transaction

Common Stock

Other

Transaction value
Shares: -2,455,744
Change %: -53%
Price: $0.000000^*
Shares after: 2,170,898
Date: 19 May 2026
Ownership: Horizon Kinetics Asset Management LLC
Footnotes: F1, F2, F3

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Section 16 status

HORIZON KINETICS ASSET MANAGEMENT LLC is no longer subject to Section 16 filing requirements. Form 4 or Form 5 obligations may still apply in specific circumstances.

Explanation of responses 3 footnotes

Footnote F1

On May 21, 2026, Horizon Kinetics Asset Management LLC ("HKAM") filed an amendment to its Schedule 13D wherein it reported beneficial ownership of 7,400,316 shares or 7.8 percent of the outstanding shares of the Issuer. The extent of HKAM's pecuniary interest in the shares reported in the Schedule 13D are disclosed herein.

Footnote F2

The change represents a reduction of 2,455,744 shares that were distributed in-kind on a pro rata basis, without consideration.

Footnote F3

This amount reflects a reduction of 7,200 shares that were held in an account for which the Reporting Person no longer has a pecuniary interest.

SEC remarks

Murray Stahl previously served as a Director of the Issuer and the Chairman, Chief Executive Officer and Chief Investment Officer of Horizon Kinetics Asset Management LLC ("HKAM") until his passing on April 7, 2026. On April 24, 2026, Eric Sites, who serves as a Managing Director of HKAM, was appointed to the Issuer's Board of Directors. Mr. Sites does not exercise investment discretion on behalf of HKAM with respect to the securities of the Issuer and is not deemed to beneficially own the securities reported herein. The extent of Mr. Sites' pecuniary interest in the securities of the Issuer are reported separately in his own filings.