UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934 (Amendment No.         )

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☐ Preliminary Proxy Statement

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☐ Definitive Proxy Statement

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☐ Soliciting Material under §240.14a-12

CSG SYSTEMS INTERNATIONAL, INC.

(Name of Registrant as Specified In Its Charter)

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*** Exercise Your Right to Vote ***Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on May 16, 2019 CSG SYSTEMS INTERNATIONAL, INC. Meeting Information Meeting Type: Annual Meeting For holders as of: March 20, 2019 Date: May 16, 2019 Time: 8:00 AM CDT Location: Sofitel Chicago Water Tower Hotel 20 East Chestnut Street Chicago, Illinois 60611 CSG SYSTEMS INTERNATIONAL, INC. 6175 S. WILLOW DRIVE GREENWOOD VILLAGE, CO 80111 You are receiving this communication because you hold shares in the above named company. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. See the reverse side of this notice to obtain proxy materials and voting instructions. 0000401758_1 R1.0.1.18

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: I. Notice & Proxy Statement 2. From 10-K How to View Online: Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX (located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 02, 2019 to facilitate timely delivery. How To Vote Please Choose One of the Following Voting Methods Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow XXXX XXXX XXXX XXXX available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. 0000401758_2 R1.0.1.18

Voting items The Board of Directors recommends you vote FOR the following: 1. Election of Directors Nominees 1a. Ronald H. Cooper 1b. Janice I. Obuchowski 1c. Donald B. Reed The Board of Directors recommends you vote FOR proposals 2 and 3. 2. To approve, on an advisory basis, the compensation of our named executive officers. 3. To ratify the appointment of KPMG LLP as our independent registered public accounting firm for fiscal 2019. NOTE: Any other business that properly comes before the meeting or any adjournment or postponement of the meeting. 0000401758_3 R1.0.1.18

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