$MIAX

$32.53 -$0.63 (1.9%) Close

$MIAX Overview Financial Statements SEC Filings Executives News Red Flags Capital Raising Ownership Insider Transactions Congressional Trades

Ownership

13F as of Q2 2026 · 99.2M shares outstanding

Who owns MIAX?

By type of holder

Institutions 69.3% Insiders 21.0% Everyone else 9.8%

Concentration Top 10 holders own 44.2%

Horizon Kinetics Asset Management LLC 7.9% · Horizon Kinetics Holding Corp 7.5%

Institutional ownership

69.3%

+18.6 pts vs last qtr

Institutional holders

203

+1 vs last qtr

Net shares bought

+18.5M

by institutions in Q2 2026

New / sold out

48 / 47

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

Horizon Kinetics Asset Management LLC +4.4M
BlackRock, Inc. +2.8M

Biggest sellers in Q2 2026

Susquehanna International Group, LLP SOLD OUT −3.3M
Citadel Advisors LLC SOLD OUT −1.6M

Who is planning to sell?

Notices of proposed sale, last 12 months

$87.4M

32 notices from 13 people

Shares covered

2.1M

2.08% of the company

Arranged in advance

100%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Gallagher Investments LLC Director 10b5-1 $33.8M
Douglas M. Schafer JR. Officer 10b5-1 $15.4M

Every notice on Red Flags →

A Form 144 is notice of a planned sale, not the sale itself. What insiders actually sold is on Insider Transactions.

Is your stake being diluted?

Diluted share count, FY2023–FY2025

+23.7%

+11.22% a year

Each share's claim on the business

−19.2%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

$37.6M vs $131M

over 3 fiscal years

Diluted shares, split-adjusted

Buybacks Stock-based comp

How patient are the owners?

Institutional shares by how long they've been held

5+ years0% 3–5 years0% 1–3 years0% Under 1 year100%

Quarterly turnover

42.8%

of institutional shares changed hands

Top 10 managers, median time held

3 quarters

Super Investors

Investment managers reporting MIAX on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
HK Horizon Kinetics Asset Management LLC 13D · 7.8%	7.8M	7.90%	+4.4M (+127.2%)	Q3 '25	3.3%
Shares held by quarter Peak holding7.8M (Q2'26) Change over 8 quarters+7.8M Share of the company7.900% Disclosed stake13D · 7.8% Horizon Kinetics Asset Management LLC's full portfolio →
B BlackRock, Inc.	5.1M	5.11%	+2.8M (+127.2%)	Q3 '25	0.0%
Shares held by quarter Peak holding5.1M (Q2'26) Change over 8 quarters+5.1M Share of the company5.110% BlackRock, Inc.'s full portfolio →

Horizon Kinetics Asset Management LLC

13D · 7.8%

7.8M

% of company

7.90%

Change vs last qtr

+4.4M (+127.2%)

Held since

Q3 '25

BlackRock, Inc.

5.1M

% of company

5.11%

Change vs last qtr

+2.8M (+127.2%)

Held since

Q3 '25

28 more super investors behind a free account

See every manager holding Miami International Holdings, Inc., how their position has changed, and how long they've held it.

Institutional Funds

Mutual funds and ETFs reporting MIAX on Form N-PORT; together they hold 28.9% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
VT Vanguard Total Stock Market Index Fund Vanguard Index Funds	$101M	2.7M	2.73%	0.00%	June 30, 2026
IR iShares Russell 2000 ETF iShares Trust	$74.1M	2.0M	2.01%	0.09%	June 30, 2026

Vanguard Total Stock Market Index Fund

Vanguard Index Funds

Position value

$101M

% of company

2.73%

% of the fund

0.00%

As of

June 30, 2026

iShares Russell 2000 ETF

iShares Trust

Position value

$74.1M

% of company

2.01%

% of the fund

0.09%

As of

June 30, 2026

23 more funds behind a free account

See every fund holding Miami International Holdings, Inc. and how much of the fund the position is.

Insiders and 5%+ holders

From Forms 3/4/5 and Schedules 13D/G

Holder	Shares	% of company	Change vs last qtr	8 quarters	Held since	% of their book
HK Horizon Kinetics Holding Corp 5%+ holder 13D · 7.8%	7.4M	7.46%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company7.460% Disclosed stake13D · 7.8% View the 13D/G filing →
TP Thomas P. Gallagher 5%+ holder 13D · 4.9%	4.0M	4.07%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company4.070% Disclosed stake13D · 4.9% View the 13D/G filing →

Horizon Kinetics Holding Corp

5%+ holder13D · 7.8%

7.4M

% of company

7.46%

Change vs last qtr

—

Held since

—

Thomas P. Gallagher

5%+ holder13D · 4.9%

4.0M

% of company

4.07%

Change vs last qtr

—

Held since

—

24 more holders behind a free account

See every insider and 5%+ holder of Miami International Holdings, Inc..

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