UNITED STATES 

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of report (Date of earliest event reported): December 18, 2017

OTTER TAIL CORPORATION

(Exact name of registrant as specified in its charter)

Registrant's telephone number, including area code: (866) 410-8780

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

__ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

__ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

__ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

__ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 or Rule 12b-2 of the Securities Exchange Act of 1934.

Emerging growth company __

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. __

Item 1.01.      Entry into a Material Definitive Agreement.

On December 18, 2017, the Board of Directors of Otter Tail Corporation approved an amendment to the Executive Restoration Plus Plan that extends the group of eligible participants from Otter Tail Corporation to Otter Tail Corporation and its affiliated companies, as those participants are approved by the Board.

Signature

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

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