BLACK HILLS BEHAVIOR, LLC

tainment of age 65, total and permanent disability, or death. Contributions — Contributions to the Plan include (i) salary reduction contributions authorized by participants, (ii) matching contributions made by the Company, (iii) non-elective contributions made by the Company; and (iv) participant rollovers from another plan. Participants may contribute up to 50 % of th eir eligible compensation to the Plan each year. These contributions are subject to certain IRC limitations with an annual maximum pre-tax contribution of $ 23,500 for 2025 and $ 23,000 for 2024. Combined employee pre-tax, employee after-tax, employee Roth and employer contributions per participant (excluding catch-up contributions) were limited to the lesser of $ 70,000 and $ 69,000 in 2025 and 2024, respectively or 50 % o

contribution portion of their accounts is based on years of service at a rate of 20 % per year. A participant is 100 % vested after five years of service. Participants also become fully vested in Company contributions if their employment with the Company is terminated due to retirement at or after attainment of age 65, total and permanent disability, or death. Contributions — Contributions to the Plan include (i) salary reduction contributions authorized by participants, (ii) matching contributions made by the Company, (iii) non-elective contributions made by the Company; and (iv) participant rollovers from another plan. Participants may contribute up to 50 % of th eir eligible compensation to the Plan each year. These contributions are subject to certain IRC limitations with an annual max

nd Vesting — Employees meeting certain criteria, as defined in the Plan, are eligible to participate in the Plan one month following their date of employment. The Plan includes an automatic enrollment provision whereby all newly eligible employees are automatically enrolled in the Plan unless they affirmatively elect not to participate in the Plan. Automatically enrolled participants have their deferral rate se t at 6 % of eligible compensation and their contributions are invested in a target retirement fund appropriate for their age until changed by the participant. The Plan includes an Automatic Savings Increase (ASI) feature where the participant’s savings rate will increase 1 % annually until their savings rate reaches 15 %, they have el ected to change their savings rate, or they have

ome 135,987,945   Other income:  Interest received on notes receivable from participants 833,025   Total additions to net assets 203,141,397   Deductions from net assets:  Administrative expenses ( 198,018 ) Benefits paid to participants ( 80,429,078 ) Total deductions from net assets ( 80,627,096 )  Increase in net assets available for benefits 122,514,301   Net assets available for benefits:  Beginning of year 811,221,284 End of year $ 933,735,585 See Notes to Financial Statements . 5 Table of Contents BLACK HILLS CORPORATION 401(k) RETIREMENT SAVINGS PLAN NOTES TO FINANCIAL STATEMENTS As of December 31, 2025 and 2024 and for the Year Ended December 31, 2025 (1) DESCRIPTION OF THE PLAN The following description of the Black Hills Corporation 401(k) Retirement Savings Plan (th