Miami International Holdings (MIAX) insider purchase and derivative holdings

Rhea-AI Filing Summary

Miami International Holdings, Inc.

The report also lists fully vested stock options held directly by the insider for 7,500, 10,000, 14,331 and 2,500 underlying shares at exercise prices between $16.14 and $25.98, as well as several currently vested warrants held indirectly through Horizon Kinetics Asset Management LLC for 24,878, 27,561, 21,290 and 38,927 underlying shares. Murray Stahl, who leads Horizon Kinetics Asset Management LLC, disclaims beneficial ownership except for any pecuniary interest.

12/15/2025 - 03:53 PM

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

STAHL MURRAY

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MIAMI INTERNATIONAL HOLDINGS, INC. [ MIAX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
12/12/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	12/12/2025		P		2,439	A	$41	4,560,364(1)(2)	I	Horizon Kinetics Asset Management LLC

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Options	$16.14(3)							08/13/2025	07/31/2031	Miami International Holdings Inc	7,500		7,500	D
Options	$25.98(3)							08/13/2025	06/30/2032	Miami International Holdings Inc	10,000		10,000	D
Options	$19.84(3)							08/13/2025	03/26/2033	Miami International Holdings Inc	14,331		14,331	D
Options	$16.14(3)							08/13/2025	05/31/2031	Miami International Holdings Inc	2,500		2,500	D
Warrants	$20.5(1)(4)							08/13/2025	11/15/2026	Miami International Holdings Inc	24,878		24,878	I	Horizon Kinetics Asset Management LLC
Warrants	$20.5(1)(4)							08/13/2025	02/05/2027	Miami International Holdings Inc	27,561		27,561	I	Horizon Kinetics Asset Management LLC
Warrants	$15(1)(4)							08/13/2025	04/08/2026	Miami International Holdings Inc	21,290		21,290	I	Horizon Kinetics Asset Management LLC
Warrants	$20.5(1)(4)							08/13/2025	10/17/2026	Miami International Holdings Inc	38,927		38,927	I	Horizon Kinetics Asset Management LLC

1. Name and Address of Reporting Person^*

STAHL MURRAY

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

HORIZON KINETICS ASSET MANAGEMENT LLC

(Last) (First) (Middle)

470 PARK AVE S

8TH FLOOR SOUTH

(Street)

NEW YORK NY 10016

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Murray Stahl serves as Chairman, Chief Executive Officer, and Chief Investment Officer of Horizon Kinetics Asset Management LLC ("HKAM"), which manages funds and accounts (the "Managed Accounts") that hold securities of the Issuer. Mr. Stahl does not exercise investment discretion with respect to the securities of the Issuer that are beneficially owned by the Managed Accounts. Mr. Stahl disclaims beneficial ownership over the securities reported, except to the extent of his pecuniary interest therein, if any. The filing of this Form shall not be deemed an admission that the Mr. Stahl is the beneficial owner of such securities for purposes of Section 16 or any other purpose.

2. Includes 5,000 shares of Series B Preferred Stock that have been converted into Common Stock on a one-for-one basis upon the closing of the Company's initial public offering and which have no expiration date and 14,998 shares of Non-Voting Common Stock that have been converted into shares of Common Stock on a one-for-one basis upon the closing of the Company's IPO and which have no expiration date.

3. The Options given to Mr. Stahl are fully vested.

4. The Warrants are currently vested and presently exercisable until the expiration date show.

	/s/Jay Kesslen, attorney in fact	12/15/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction was reported for MIAX (Miami International Holdings)?

An insider group associated with Horizon Kinetics Asset Management LLC reported purchasing 2,439 shares of Miami International Holdings common stock on 12/12/2025 at a price of $41 per share, as an indirect acquisition.

How many MIAX shares are beneficially owned after this insider purchase?

After the reported transaction, the insider group indirectly beneficially owns 4,560,364 shares of Miami International Holdings common stock through Horizon Kinetics Asset Management LLC-managed accounts.

Who is the reporting person in this MIAX insider transaction and what is the relationship to the issuer?

The report identifies a relationship as Director and 10% Owner of Miami International Holdings. The explanation notes that Murray Stahl serves as Chairman, Chief Executive Officer, and Chief Investment Officer of Horizon Kinetics Asset Management LLC, which manages accounts holding the issuer’s securities.

What derivative securities related to MIAX does the insider hold?

The insider directly holds fully vested stock options over 7,500, 10,000, 14,331 and 2,500 Miami International Holdings shares with exercise prices including $16.14, $25.98 and $19.84. In addition, several warrants are held indirectly through Horizon Kinetics Asset Management LLC over 24,878, 27,561, 21,290 and 38,927 shares at exercise prices including $20.5 and $15, each with specified expiration dates.

Are the MIAX options and warrants reported in this insider filing vested?

According to the explanation, the options given to Murray Stahl are fully vested, and the warrants reported are currently vested and presently exercisable until their respective expiration dates.

What special share classes are included in the MIAX beneficial ownership total?

The indirect beneficial ownership total includes 5,000 shares of Series B Preferred Stock and 14,998 shares of Non-Voting Common Stock, all of which have been converted into common stock on a one-for-one basis upon the closing of the company’s initial public offering and have no expiration date.

Does Murray Stahl claim full beneficial ownership of all reported MIAX securities?

No. The explanation states that Murray Stahl disclaims beneficial ownership of the securities held by the managed accounts, except to the extent of his pecuniary interest, if any, and that the report is not an admission of beneficial ownership for Section 16 or other purposes.