# EDGAR Filing Document

**Accession Number:** 0001466593
**File Stem:** 0001466593-26-000059
**Filing Date:** 2026-5
**Character Count:** 12443
**Document Hash:** 66c145f5d1dc6f450d4eb65daedab9d9
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001466593-26-000059.hdr.sgml**: 20260529

**ACCESSION NUMBER**: 0001466593-26-000059

**CONFORMED SUBMISSION TYPE**: SD

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260529

**DATE AS OF CHANGE**: 20260529

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Otter Tail Corp
- **CENTRAL INDEX KEY:** 0001466593
- **STANDARD INDUSTRIAL CLASSIFICATION:** ELECTRIC SERVICES [4911]
- **ORGANIZATION NAME:** 01 Energy & Transportation
- **EIN:** 270383995
- **STATE OF INCORPORATION:** MN
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SD
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 000-53713
- **FILM NUMBER:** 261041024

**BUSINESS ADDRESS:**
- **STREET 1:** 215 S CASCADE ST
- **STREET 2:** PO BOX 496
- **CITY:** FERGUS FALLS
- **STATE:** MN
- **ZIP:** 56538-0496
- **BUSINESS PHONE:** 866-410-8780

**MAIL ADDRESS:**
- **STREET 1:** 215 S CASCADE ST
- **STREET 2:** PO BOX 496
- **CITY:** FERGUS FALLS
- **STATE:** MN
- **ZIP:** 56538-0496

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Otter Tail Holding Co
- **DATE OF NAME CHANGE:** 20090618

**UNITED STATES** 

**SECURITIES AND EXCHANGE COMMISSION**

**WASHINGTON, D.C. 20549**

**FORM SD**

**SPECIALIZED DISCLOSURE REPORT** 

**OTTER TAIL CORPORATION**

(Exact name of registrant as specified in its charter)

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| | | |
|:---|:---|:---|
| **Minnesota**<br>(State or other jurisdiction of incorporation or organization) | **0-53713**<br>(Commission File Number) | **27-0383995**<br>(I.R.S. Employer Identification No.) |

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**215 South Cascade Street, P.O. Box 496, Fergus Falls, MN 56538-0496**

(Address of principal executive offices, including zip code)

**Jennifer O. Smestad, Esq.**

**Senior Vice President, General Counsel and Corporate Secretary**

**215 South Cascade Street, Box 496**

**Fergus Falls, Minnesota 56538-0496**

**(866) 410-8780**

(Name and telephone number, including area code, of the person to contact in connection with this report)

**Check the appropriate box to indicate the rule pursuant to which this form is being filed, and provide the period to which the information in this form applies:**

**☒** **Rule 13p-1 under the Securities Exchange Act (17 CFR 240.13p-1) for the reporting period from January 1 to December 31, 2025.**

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**Section 1.01 and 1.02 – Conflicts Minerals Disclosure**

**Items 1.01 and 1.02 – Conflicts Minerals Disclosure and Report Exhibit**

This Form SD and the Conflict Minerals Report, filed as Exhibit 1.01 hereto, are publicly available on our website under Investors, SEC Filings, Form SD at the website www.ottertail.com as well as the SEC's EDGAR database at www.sec.gov. The content of any website referred to in this Form SD is included for general information only and is not incorporated by reference in this Form SD.

**Section 2 - Exhibits**

**Item 2.01 &nbsp;&nbsp;&nbsp;&nbsp;<u>Exhibits</u>**

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1.01&nbsp;&nbsp;&nbsp;&nbsp;<u>[Conflict Minerals Report for the reporting period January 1, 202](exhibit101-conflictmineral.htm)[5](exhibit101-conflictmineral.htm)[to December 31, 202](exhibit101-conflictmineral.htm)</u>5 as required by Items 1.01 and 1.02 of this Form SD.

**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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| | | |
|:---|:---|:---|
| | OTTER TAIL CORPORATION | OTTER TAIL CORPORATION |
| Date: May 29, 2026 | By: | /s/ Jennifer O. Smestad |
|  |  | Jennifer O. Smestad |
|  |  | Senior Vice President, General Counsel and Corporate Secretary |

---

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

## Exhibit 1.01

**Exhibit 1.01**

**Conflict Minerals Report**

**Otter Tail Corporation**

**For the Year Ended December 31, 2025**

**Introduction**

This report for the year ended December 31, 2025, is made by Otter Tail Corporation (the "Company") in compliance with Rule 13p-1 under the Securities Exchange Act of 1934 (the "Rule"). The Rule was adopted by the Securities and Exchange Commission ("SEC") to implement reporting and disclosure requirements related to conflict minerals as directed by the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (Dodd-Frank Act). The Rule imposes certain reporting obligations on SEC registrants whose manufactured products contain conflict minerals that are necessary to the functionality or production of their products. Conflict minerals are defined as cassiterite, columbite-tantalite, gold, wolframite and their derivatives, which are limited to tin, tantalum, tungsten and gold ("3TG"). These requirements apply to registrants regardless of the geographic origin of the conflict minerals and whether or not the trading in those minerals benefits armed groups.

If a registrant has reason to believe that any of the conflict minerals in its supply chain may have originated in the Democratic Republic of the Congo ("DRC") or an adjoining country (the "Covered Countries"), or a registrant is unable to determine the country of origin of those conflict minerals, then the registrant must exercise due diligence on the source and chain of custody of those conflict minerals. The registrant must annually submit a specialized disclosure ("Form SD") and Conflict Minerals Report ("CMR") to the SEC that includes a description of those due diligence measures.

The Company has subsidiary companies operating on two platforms, electric and manufacturing. The Company's electric utility subsidiary operates in three states serving over 400 communities. The Company's subsidiary companies in its manufacturing platform provide metal fabrication services, thermoformed and extruded plastic products as well as polyvinyl chloride ("PVC") pipe manufacturing. Of the products produced by the Company, conflict minerals, particularly tin, is necessary to the functionality or production of PVC pipe. The Company's two PVC pipe companies have two suppliers which supply them with the product containing tin. The compound containing tin used in the manufacture of PVC pipes may not be subject to the Rule because the compounds are chemically distinct from metals.

**Management Systems**

The Company's policy and procedure are guided by the limited use of conflict minerals. Its goals are to hold itself and suppliers accountable for responsibly sourcing conflict minerals. The goals are reasonable and achievable. Based on the Company's limited use of conflict minerals and the prior Reasonable Country of Origin Inquiries ("RCOI"), the Company has relied on its guiding principles - particularly its commitment to integrity, people and communities to form the basis for its program.

The Company's internal team consists of relevant subject matter experts from the functional areas including legal, accounting, and procurement within its various companies.

The Company has established a system to engage relevant first-tier suppliers, who provide materials containing conflict minerals. With the limited number of suppliers, the transparency of the supply chain allows the identification of all smelters in the supply chain in most instances. Additionally, the Company's subsidiary companies which do not use conflict minerals, but are involved in metal fabrication, monitor their supply chain for conflict minerals.

The Company has enlisted the assistance of its relevant suppliers to execute its conflict minerals program. The Company has set expectations with regard to its suppliers through its disclosure requirements to ensure compliance with obtaining the required information necessary to support the Company's compliance with the Rule. The Company's relationships with its suppliers have been instrumental in helping the Company meet the requirements of the Rule and the Organization for Economic Co-operation and Development ("OECD") guidance.

**Identify and Assess Risks in Supply Chain**

We conducted our surveys using our suppliers' Conflict Minerals Reporting Template ("CMRT"). We used the CMRT to identify smelter or refiner facilities and countries of origin of our necessary conflict minerals. The Company relied on the Responsible Mineral Initiative ("RMI") and other information provided by our suppliers to identify countries of origin for Responsible Minerals Assurance Process ("RMAP") compliant smelter or refiner facilities. The Company reviewed the responses from the CMRT questionnaires with our supply chain department and cross checked the list with RMAP facilities.

**Reasonable Country of Origin Inquiry**

The Company is many steps removed from the mining of conflict minerals. The Company has conducted an analysis of our products and found that, although we do not directly purchase minerals from our suppliers, we do purchase materials that contain conflict minerals, particularly identified as tin. We rely on our Tier 1 suppliers to provide information on the origin of the tin contained in materials necessary to the functionality or production of our products by utilizing the CMRT of the RMI, which allows us to perform our RCOI.

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**Due Diligence**

The Company's due diligence is designed to conform to the OECD framework. The Company's due diligence process includes requesting its supplier of products containing tin to complete the CMRT survey in order to obtain information about the smelters or refiners in the Company's supply chain. The Company has determined that these actions represent the most reasonable effort the Company can make to determine the mines or locations of origin of the 3TG minerals in our supply chain.

The Company's two suppliers provided lists of all the smelters used in their supply chains. These suppliers represented that all of the smelters on their smelter list are on the list of smelters conformant with the relevant RMAP assessment protocol. The Company used public sources to confirm that the smelters listed are compliant with the relevant RMAP assessment protocol.

**Determination**

Based on the information provided by the Company's suppliers, and the independent diligence process, the Company believes the facilities that have been used to process the tin used in the production of its PVC pipe products include RMAP assessment protocol smelters listed in Appendix I below.

**Steps for Risk Mitigation**

The Company plans to continue the following practices to mitigate the risk that the material containing conflict minerals necessary to the functionality or production of its products does not benefit armed groups in the Covered Countries:

&nbsp;&nbsp;&nbsp;&nbsp;1.Continue to have communications with relevant suppliers and customers to understand their requests and any of their concerns regarding compliance in satisfying the Rule.

&nbsp;&nbsp;&nbsp;&nbsp;2.Continue using current processes within the Company's supply chain organization in working with suppliers to obtain required information.

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**APPENDIX I**

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| | | | |
|:---|:---|:---|:---|
| | **Mineral** | **Smelter Name** | **Country Location of Smelter** |
| CID001105 | Tin | Malaysia Smelting Corporation (MSC) | MALAYSIA |
| CID003582 | Tin | Fabrica Auricchio | BRAZIL |
| CID001182 | Tin | Minsur | PERU |
| CID001173 | Tin | Mineracao Taboca S.A. | BRAZIL |
| CID003387 | Tin | Luna Smelter, Ltd. | RWANDA |
| CID001482 | Tin | PT Timah Tbk Mentok | INDONESIA |
| CID005067 | Tin | PT Arsed Indonesia | INDONESIA |
| CID000438 | Tin | Empresa Metalurgica (EM) Vinto | BOLIVIA |
| CID001337 | Tin | Operaciones Metalurgicas S.A. | BOLIVIA |
| CID002036 | Tin | White Solder Metalurgia e Mineraco Ltda. | BRAZIL |
| CID003504 | Tin | Conecsus LLC | UNITED STATES OF AMERICA |
| CID002593 | Tin | PT Rajehand Ariq | INDONESIA |
| CID003449 | Tin | PT Mitra Sukses Globalindo | INDONESIA |

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