[Form 4] CoStar Group Inc Insider Trading Activity

Rhea-AI Filing Summary

Saint Frederick G., identified as President, Marketplaces of CoStar Group, Inc. (CSGP), reported a sale of 25,000 shares of CoStar common stock on 08/28/2025 at an average price of $90.33 per share (sale prices ranged $90.30–$90.38). Following the transaction the reporting person beneficially owned 293,103 shares, held directly. The Form 4 was signed by attorney-in-fact Gene Boxer on 09/02/2025. The filing shows routine insider disposition with the required Section 16 disclosure and includes an explanatory remark on the average sale price.

Positive

• Timely and clear disclosure of an insider transaction on Form 4, including transaction date, price range, and post-sale ownership
• Complete post-transaction ownership reported: 293,103 shares held directly

Negative

• Insider sale of 25,000 shares, which decreases the officer's direct holdings
• No information provided about the purpose of the sale (e.g., diversification, tax, or other), so intent is unspecified

Insights

Securities Analyst

TL;DR Insider officer sold a modest block of shares, reducing direct holdings to 293,103 shares; transaction was disclosed on Form 4.

The sale of 25,000 shares at an average price of $90.33 represents a routine insider disposition rather than a control change or a large, dilutive event. The filing clearly states the transaction date and post-sale ownership, and includes the required price-range explanation. For investors, this is a transparent disclosure but not, by itself, a material corporate event that alters capital structure or governance.

Corporate Governance Expert

TL;DR Officer sale properly reported; no indications of related-party transfers or changes to officer status.

The Form 4 identifies the reporting person as a company officer and records a direct sale with an explicit price range and resulting share count. The signature by an attorney-in-fact and inclusion of explanatory remarks meet procedural requirements. There is no information in the filing indicating any compensatory, plan-based or derivative transaction, nor any amendment or correction to prior disclosures.

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^*

SAINT FREDERICK G.

(Last) (First) (Middle)

C/O COSTAR GROUP, INC.

1201 WILSON BLVD.

(Street)

ARLINGTON VA 22209

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
COSTAR GROUP, INC. [ CSGP ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
08/28/2025

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

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

X	Form filed by One Reporting Person
	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, par value $0.01 per share	08/28/2025		S		25,000	D	$90.33(1)	293,103	D

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. Average based on sales prices ranging from $90.30 to $90.38.

Remarks:

	/s/ Gene Boxer, Attorney-in-Fact	09/02/2025
	** 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 did the CoStar Group (CSGP) insider sell?

The reporting person sold 25,000 shares of CoStar common stock on 08/28/2025 at an average price of $90.33 per share.

Who filed the Form 4 for CSGP and what is their role?

The Form 4 was filed for Saint Frederick G., identified as President, Marketplaces of CoStar Group, Inc.

How many CoStar shares does the reporting person own after the sale?

Following the reported transaction the reporting person beneficially owned 293,103 shares, held directly.

When was the Form 4 signed and by whom?

The form bears a signature by attorney-in-fact Gene Boxer dated 09/02/2025.

What sale price range was disclosed on the Form 4?

The average sale price reported was $90.33, with sale prices ranging from $90.30 to $90.38.