Black Hills Corporation filed a Form 8-K with the SEC on August 17, 2026, providing historical financial statements of NorthWestern Energy Group, Inc. and unaudited pro forma combined financial information in connection with the companies' pending all-stock merger.

Key Highlights

  • Merger Agreement date: Black Hills and NorthWestern Energy Group entered into an Agreement and Plan of Merger on August 18, 2025, as previously disclosed.
  • Board approval: The Merger Agreement was unanimously approved on August 18, 2025 by the boards of both Black Hills and NorthWestern, according to the filing.
  • Deal structure: The transaction is described as an all-stock business combination, with River Merger Sub Inc. named as a direct wholly owned subsidiary of Black Hills.
  • Pro forma basis dates: The pro forma combined condensed statement of income is presented as if the merger were completed on January 1, 2025, and the pro forma combined condensed balance sheet as if completed on June 30, 2026.
  • NorthWestern financials: Exhibit 99.1 contains unaudited consolidated financial statements of NorthWestern Energy Group as of and for the six months ended June 30, 2026 and 2025.
  • Pending conditions: The merger remains subject to regulatory approvals, including from certain state regulatory commissions and the Federal Energy Regulatory Commission.

Black Hills and NorthWestern Pending Merger: Financial Filings Explained

Black Hills Corporation (NYSE:BKH), headquartered in Rapid City, South Dakota, filed this Current Report on August 17, 2026 to provide supplemental financial information related to its pending combination with NorthWestern Energy Group, Inc. According to the filing, the report was made "solely to provide certain information relating to the pending merger transaction." The Merger Agreement, signed August 18, 2025, calls for an all-stock business combination and involves River Merger Sub Inc., a Delaware corporation and direct wholly owned subsidiary of Black Hills.

The filing includes two exhibits. Exhibit 99.1 contains unaudited consolidated financial statements of NorthWestern Energy Group as of and for the six months ended June 30, 2026 and 2025. The filing notes these statements "were prepared by NorthWestern and previously disclosed by NorthWestern in its periodic reports" and have not been independently validated or reviewed by Black Hills. Exhibit 99.2 contains unaudited pro forma combined condensed financial information prepared under Article 11 of Regulation S-X, reflecting pro forma adjustments related to the pending transaction.

The filing states that the pro forma information "has been prepared for illustrative purposes only" and "does not purport to be indicative of what the combined company's consolidated financial position or results of operations actually would have been." It further notes the pro forma information "does not purport to project the future financial position or operating results of the combined company." The filing also contains forward-looking statements, which the company indicates are intended to rely on safe harbor protections under the Private Securities Litigation Reform Act of 1995 and are subject to numerous stated risks and uncertainties, including potential delays or failure to obtain required regulatory approvals.

What Was Disclosed

Black Hills Corporation filed supplemental merger-related financial information, including NorthWestern Energy Group's historical interim financial statements and unaudited pro forma combined financial data, in connection with the companies' pending all-stock merger announced August 18, 2025.