MIAX CEO reports tax-withholding share disposition

MIAMI INTERNATIONAL HOLDINGS, INC.

Rhea-AI Filing Summary

MIAMI INTERNATIONAL HOLDINGS, INC. Chairman & CEO Thomas P. Gallagher reported an indirect tax-withholding disposition of 20,875 shares of Common Stock on March 30, 2026. The shares, held by Gallagher Investments, LLC, were surrendered to the company at $37.50 per share to cover tax obligations from restricted stock awards and did not involve an open-market sale. Following this transaction, indirect holdings reported through Gallagher Investments, LLC totaled 1,827,399 shares of Common Stock, over which Mr. Gallagher maintains beneficial ownership with voting and dispositive control.

Insider Trade Summary

Exercise Price or Tax Liability: 20,875 shares

Exercise Price or Tax Liability 1 txn

Insider Gallagher Thomas P.

Role Chairman & CEO

Type	Security	Shares	Price	Value
Exercise Price or Tax Liability	Common Stock	20,875	$37.50	$783K

Holdings After Transaction: Common Stock — 1,827,399 shares (Indirect, By Gallagher Investments, LLC)

Footnotes (2)

1. F1. Represents shares that have been surrendered to the Company to satisfy tax withholding and remittance obligations in connection with the net settlement of restricted stock awards and does not represent a sale by the reporting person.
2. F2. Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC.

Key Figures

Shares surrendered for tax withholding: 20,875 shares Per-share value for surrender: $37.50 per share Indirect holdings after transaction: 1,827,399 shares +1 more

4 metrics

Shares surrendered for tax withholding 20,875 shares Common Stock surrendered on March 30, 2026

Per-share value for surrender $37.50 per share Value used to satisfy tax obligations

Indirect holdings after transaction 1,827,399 shares Common Stock held via Gallagher Investments, LLC after disposition

Tax-withholding disposition shares 20,875 shares transactionSummary taxWithholdingShares

Key Terms

tax-withholding disposition, restricted stock awards, beneficial ownership, indirect ownership

4 terms

tax-withholding disposition financial

"transaction_action: "tax-withholding disposition" for 20,875 shares of Common Stock"

A tax-withholding disposition is an event or transaction—such as selling or transferring securities, exercising options, or receiving compensation—that triggers a requirement to hold back part of the payment and remit it to tax authorities. It matters to investors because it reduces the cash they receive immediately and can change the timing and amount of taxable income, like a cashier taking a portion of your sale proceeds to pay taxes before you get the rest.

restricted stock awards financial

"in connection with the net settlement of restricted stock awards and does not represent a sale"

Restricted stock awards are company shares given to employees or executives that cannot be sold or transferred until certain conditions — like staying with the company for a set time or meeting performance targets — are met, like a gift that is locked in a safe until rules are satisfied. Investors care because these awards tie management’s pay to company performance, can increase the number of shares outstanding when they become tradable (dilution), and may signal expected future selling pressure or commitment to long-term growth.

beneficial ownership financial

"Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC."

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

indirect ownership financial

"ownership_type: "indirect" and nature_of_ownership: "By Gallagher Investments, LLC""

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did MIAX Chairman & CEO Thomas P. Gallagher report?

Thomas P. Gallagher reported a tax-withholding disposition of 20,875 MIAX Common Stock shares. These shares were surrendered to the company to cover tax obligations arising from restricted stock awards, rather than sold on the open market for investment purposes.

At what price were the MIAX shares surrendered in the Gallagher Form 4 filing?

The surrendered MIAX Common Stock shares were valued at $37.50 per share. This value was used to satisfy tax withholding and remittance obligations connected to the net settlement of restricted stock awards, according to the disclosure and related footnotes.

How many MIAX shares does Gallagher Investments, LLC hold after this transaction?

After the reported tax-withholding disposition, Gallagher Investments, LLC holds 1,827,399 MIAX Common Stock shares. The filing states that Thomas P. Gallagher maintains beneficial ownership, including voting and dispositive control, over Gallagher Investments, LLC and its reported holdings.

Was the MIAX insider transaction a market sale of shares?

The transaction was not a market sale of MIAX shares. The filing explains that 20,875 shares were surrendered back to the company solely to satisfy tax withholding and remittance obligations related to restricted stock awards, and it explicitly notes this does not represent a sale.

How is the MIAX insider ownership held in the reported Form 4?

The MIAX Common Stock is held indirectly through Gallagher Investments, LLC. The filing classifies ownership as indirect and notes that Thomas P. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC and its reported share position.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/01/2026 - 04:42 PM Learn about SEC filing dates

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^*

Gallagher Thomas P.

(Last) (First) (Middle)

C/O MIAMI INTERNATIONAL HOLDINGS, INC

7 ROSZEL ROAD, SUITE 1A

(Street)

PRINCETON NEW JERSEY 08540

(City) (State) (Zip)

UNITED STATES

(Country)

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
X	Officer (give title below)		Other (specify below)
	Chairman & CEO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/30/2026

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

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

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

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	03/30/2026		F		20,875(1)	D	$37.5	1,827,399	I(2)	By Gallagher Investments, LLC(2)

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

Explanation of Responses:

1. Represents shares that have been surrendered to the Company to satisfy tax withholding and remittance obligations in connection with the net settlement of restricted stock awards and does not represent a sale by the reporting person.

2. Mr. Gallagher maintains beneficial ownership, including dispositive and voting control, over Gallagher Investments, LLC.

Remarks:

	/s/Alessandra Maria Corona Henriques, Attorney-in-Fact	04/01/2026
	** 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.
* Form 4: SEC 1474 (03-26)