COSTAR GROUP, INC.

In addition to the other information set forth in this Report, you should carefully consider the factors disclosed in Part I, Item 1A, “Risk Factors” in our 2025 Form 10-K, which could materially affect our business, financial condition, or future results. Additional risks and uncertainties not currently known to us, or that we currently deem to be immaterial, may also have a material adverse effect on our business, financial condition, and/or results of operations. Other than the following items, there have not been any material changes to the risk factors as previously disclosed in Part I, Item 1A, "Risk Factors” in our 2025 Form 10-K.

Risks related to our business

We may be unable to realize the benefits of the Zonda Acquisition, which could have an adverse effect on us.

On May 28, 2026, we announced that we had entered into the Zonda Agreement, to acquire Zonda, and on August 21, 2026, we announced that we completed the acquisition of Zonda.

Following the acquisition, it is possible that there could be a loss of key employees, higher than expected costs, diversion of management attention, or the disruption of our ongoing businesses, which may adversely affect the combined company’s ability to maintain relationships with customers, suppliers, and employees or to achieve the anticipated benefits of the Zonda Acquisition.

We have incurred, and we will continue to incur, transaction fees, including legal, regulatory, and other costs associated with closing the Zonda Acquisition, as well as expenses related to formulating and implementing integration plans, including systems consolidation costs and employment-related costs. We may be unable to offset transaction and integration-related costs with the realization of other efficiencies related to the integration of the business.

The success of the Zonda Acquisition will depend in part on our ability to realize the anticipated business opportunities and growth prospects from combining our business with that of Zonda. We may never realize these business opportunities and growth prospects. Integrating operations and employees will require significant efforts and expenditures. If we are unable to successfully integrate Zonda’s business with ours, we may be unable to realize the growth, synergies, and other anticipated benefits resulting from the Zonda Acquisition and our business could be adversely affected.

We may be unable to complete the acquisition of Vexcel or otherwise realize the benefits of the pending Vexcel Acquisition, which could have an adverse effect on us.

On October 26, 2026, we announced that we had entered into the Merger Agreement, to acquire Vexcel. Pursuant to the Merger Agreement, and subject to the terms and conditions contained therein, at the closing of the Merger, among other things, we will acquire all of the issued and outstanding capital stock of Vexcel in a cash transaction. The closing of the Vexcel Acquisition is subject to certain customary closing conditions, including, among others: expiration or termination of the applicable waiting periods under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, and certain other regulatory laws; the absence of any law, order, decree, ruling, or injunction of a governmental authority with jurisdiction prohibiting or making illegal the consummation of the Vexcel Acquisition; the accuracy of each party’s representations and warranties and the performance and compliance by each party with its respective covenants in each case subject to certain qualifiers; there not having occurred since the date of the Merger Agreement any event, development, change, or occurrence that has had or would reasonably be expected to have had, individually or in the aggregate, a material adverse effect; and the delivery of customary closing documents. Until the completion of the Vexcel Acquisition, we will operate independently of Vexcel. It is possible that the pendency of the Vexcel Acquisition could result in the loss of key employees, higher than expected costs, diversion of management attention, or the disruption of our ongoing businesses, which may adversely affect the combined company’s ability to maintain relationships with customers, vendors, and employees or to achieve the anticipated benefits of the Vexcel Acquisition. We have incurred, and we will continue to incur, transaction fees, including legal, regulatory, and other costs associated with closing the Vexcel Acquisition, as well as expenses related to formulating and implementing integration plans, including systems consolidation costs and employment-related costs. We may be unable to offset transaction and integration- related costs with the realization of other efficiencies related to the integration of the business. The success of the Vexcel Acquisition, if completed, will depend in part on our ability to realize the anticipated business opportunities and growth prospects from combining our business with that of Vexcel. We may never realize these business opportunities and growth prospects. Integrating operations and employees will require significant efforts and expenditures. If we are unable to successfully or timely acquire and integrate Vexcel’s business with ours, we may be unable to realize the growth, synergies, and other anticipated benefits resulting from the Vexcel Acquisition and our business could be adversely affected.