Form DEFA14A - Additional definitive proxy soliciting materials and Rule 14(a)(12) material

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. )

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 Pursuant to §240.14a-12

OTTER TAIL CORPORATION

(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 all boxes that apply):

☑   No fee required

☐   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

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