[Form 4] CoStar Group Inc Insider Trading Activity

Rhea-AI Filing Summary

Insider purchase disclosed: Director Louise S. Sams acquired 3,291 shares of CoStar Group, Inc. (CSGP) on 09/09/2025 at no reported cash price and now beneficially owns 19,409 shares. The Form 4 was signed by an attorney-in-fact on 09/11/2025. The filing indicates the transaction was by the reporting person as a director and was filed individually.

Positive

• Director purchase reported: Louise S. Sams acquired 3,291 shares, increasing her beneficial ownership to 19,409 shares
• Timely Section 16 disclosure: Form 4 filed and signed by attorney-in-fact, meeting reporting requirements

Negative

• None.

Insights

Securities Analyst

TL;DR: A director reported a purchase of 3,291 shares, increasing her stake to 19,409 shares; transaction appears routine and non-priced on the form.

The Form 4 shows Louise S. Sams, a director of CoStar Group (CSGP), acquired 3,291 shares on 09/09/2025 and holds 19,409 shares following the trade. The filing lists the reporter as a director and was filed individually. No purchase price is reported on the form (price shown as $0), and no derivative transactions are disclosed. This appears to be a straightforward non-derivative acquisition recorded on Form 4.

Corporate Governance Expert

TL;DR: Director-level insider reported a small common-stock acquisition; disclosure is timely and conforms to Section 16 reporting.

The disclosure identifies Louise S. Sams as the reporting director and records a non-derivative acquisition of 3,291 common shares, bringing beneficial ownership to 19,409 shares. The form is signed by an attorney-in-fact. There are no amendments indicated and no indications of trading pursuant to a Rule 10b5-1 plan on the face of the filing. From a governance perspective, the filing meets required Section 16 disclosure elements presented in the document.

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^*

Sams Louise S

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
09/09/2025

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	09/09/2025		A		3,291	A	$0	19,409	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:

Remarks:

	/s/ Gene Boxer, Attorney-in-Fact	09/11/2025
	** 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 Form 4 for CSGP report?

The Form 4 reports that director Louise S. Sams acquired 3,291 shares of CoStar Group (CSGP) on 09/09/2025, bringing her beneficial ownership to 19,409 shares.

Was a purchase price disclosed on the Form 4 for CSGP?

The form lists the price as $0; no monetary purchase price is provided in the reported transaction details.

Does the filing indicate the transaction was part of a 10b5-1 plan?

The filing does not indicate that the transaction was made pursuant to a Rule 10b5-1(c) plan on the face of the provided content.

Who signed the Form 4 for the insider transaction at CSGP?

The Form 4 was signed by /s/ Gene Boxer, Attorney-in-Fact on 09/11/2025.

Did the Form 4 disclose any derivative transactions for CSGP?

No. Table II for derivative securities contains no reported transactions in the provided filing.