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

Filed by the Registrant ☒
Filed by a Party other than the Registrant ☐
Check the appropriate box:
☐	Preliminary Proxy Statement
☐	Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))
☐	Definitive Proxy Statement
☒	Definitive Additional Materials
☐	Soliciting Material Under §240.14a-12

BLACKLINE, INC.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):
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☐	Fee paid previously with preliminary materials.
☐	Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

Your Vote Counts! *Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V35584-P01864 BLACKLINE, INC. 21300 VICTORY BLVD, 12TH FLOOR WOODLAND HILLS, CA 91367 BLACKLINE, INC. 2024 Annual Meeting Vote by May 8, 2024 11:59 p.m. ET You invested in BLACKLINE, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy material for the shareholder meeting to be held on May 9, 2024. Vote Virtually at the Meeting* May 9, 2024 9:00 a.m. PT Virtually at: www.virtualshareholdermeeting.com/BL2024 Get informed before you vote View the Notice and Proxy Statement and Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to April 25, 2024. If you would like to request a copy of the material(s) for this and/or future shareholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy.

Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. Voting Items Board Recommends V35585-P01864 THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming shareholder meeting. Please follow the instructions on the reverse side to vote these important matters. Vote at www.ProxyVote.com 1. Election of Directors For Nominees: 01) Owen Ryan 02) Sophia Velastegui 03) William Wagner 2. To ratify the appointment of PricewaterhouseCoopers LLP (“PwC”) as the Company’s independent registered public accounting firm for its fiscal year ending December 31, 2024. For 3. Approval, on a non-binding, advisory basis, of the 2023 compensation of the Company’s named executive officers. For NOTE: In their discretion, the proxies are authorized to vote upon such other business as may properly come before the Annual Meeting of Shareholders or any adjournments or postponements thereof.