ONEOK INC /NEW/

Retirement and Other Postretirement Benefit Plans

ONEOK Retirement Plan - We maintain the ONEOK Retirement Plan, a defined benefit pension plan covering certain legacy ONEOK employees, which closed to new participants in 2005. In addition, we have a supplemental executive retirement plan for the benefit of certain officers who participate in the ONEOK Retirement Plan. Our supplemental executive retirement plan is closed to new participants. We fund our defined benefit pension plan at a level needed to maintain or exceed the minimum funding levels required by the Employee Retirement Income Security Act of 1974, as amended.

Magellan Retirement Plans - As a result of the Magellan Acquisition in 2023, we assumedtwo defined benefit pension plans covering certain legacy Magellan employees, including the Magellan Pension Plan, which closed to new participants upon the closing of the acquisition, and the Magellan Pension Plan for USW Employees, which closed to new participants in January 2024. We fund these defined benefit pension plans at a level needed to maintain or exceed the minimum funding levels required by the Employee Retirement Income Security Act of 1974, as amended.

Other Postretirement Benefit Plans - We sponsor health and welfare plans that provide postretirement medical and life insurance benefits to certain legacy ONEOK employees hired prior to 2017 and certain legacy Magellan employees who retire after a specified age with at least five years of service and satisfy certain other conditions. The postretirement medical plan for pre-Medicare participants is contributory, with retiree contributions adjusted periodically, and contains other cost-sharing features such as deductibles and coinsurance. The postretirement medical plan for Medicare-eligible participants is an account-based plan under which participants may elect to purchase private insurance policies under a private exchange and/or seek reimbursement of other eligible medical expenses and is not available to legacy Magellan employees.

Obligations and Funded Status -The following table sets forth our retirement and other postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated:

(a) - The benefit obligation for Retirement Benefits at December 31, 2025 and 2024, included the supplemental executive retirement plan obligation.

(b) - Fair value of plan assets for Retirement Benefits excluded the assets of our supplemental executive retirement plan, which totaled $90 million and $92 million at December 31, 2025 and 2024, respectively, and are included in other assets on the Consolidated Balance Sheets. These assets are maintained in a rabbi trust and are not treated as assets of the supplemental executive retirement plan.

The accumulated benefit obligation for our retirement plans was $648 million and $628 million at December 31, 2025 and 2024, respectively.

The components of net periodic benefit cost and related assumptions, and amounts recognized in other comprehensive income related to our retirement and other postretirement benefit plans are not material. The balance in accumulated other comprehensive loss at December 31, 2025 and 2024, was $46 million and $58 million, respectively. This balance is expected to be amortized over the average remaining service period of employees participating in these plans.

Actuarial Assumptions -The following table sets forth the weighted-average assumptions used to determine benefit obligations for retirement and other postretirement benefits for the periods indicated:

(a) - This actuarial assumption is only applicable to the pension plans assumed with the Magellan Acquisition.

We determine our discount rates annually utilizing portfolios of high-quality bonds matched to the estimated benefit cash flows of our retirement and other postretirement benefit plans. Bonds selected to be included in the portfolios are only those rated by S&P or Moody’s as an AA or Aa2 rating or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.

Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment allocation for our ONEOK Retirement Plan follows a glide path approach of liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. A majority of the assets of the Magellan Pension Plan and the Magellan Pension Plan for USW Employees are allocated to fixed income securities and invested to match the duration of the plans’ short, intermediate and long-term liabilities, with the remaining amount allocated to equity securities. Our pension plans utilize a diversified mix of investments that may include domestic and international equities, short, intermediate and long-term corporate and government obligations, real estate and hedge funds. The combined target allocation for the assets of our pension plans as of December 31, 2025, is as follows:

As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above.

The fair value of the plan assets for our other postretirement benefit plans as of December 31, 2025, are not material. The following tables set forth the plan assets by fair value category as of the measurement date for our defined benefit pension plans:

(a) - This category represents securities of the respective market sector from diverse industries.

(b) - This category represents bonds from diverse industries.

(c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There wereno unfunded capital commitments. These limited partnerships invest through multi-strategy programs in broadly diversified portfolios of private investment funds, hedge funds and/or separate accounts to seek equity-like returns with low market correlation, reduced volatility and limited risk.

(d) - Plan asset investments measured at fair value using the net asset value per share.

(a) - This category represents securities of the respective market sector from diverse industries.

(b) - This category represents bonds from diverse industries.

(c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There wereno unfunded capital commitments. These limited partnerships invest through multi-strategy programs in broadly diversified portfolios of private investment funds, hedge funds and/or separate accounts to seek equity-like returns with low market correlation, reduced volatility and limited risk.

(d) - Plan asset investments measured at fair value using the net asset value per share.

Contributions - During 2025, we contributed $9 million to our ONEOK Retirement Plan, $17 million to our Magellan Pension Plan and $3 million to our Magellan Pension Plan for USW Employees, all of which were related to the 2024 plan year. We donot expect contributions to our defined benefit pension plans to be material in 2026. We donot expect to make any contributions to other postretirement benefit plans in 2026.

Pension and Other Postretirement Benefit Payments - Benefit payments for our defined benefit pensions and other postretirement benefit plans for the period ending December 31, 2025, were $38 million and $4 million, respectively. The following table sets forth the defined benefit pension and other postretirement benefits payments expected to be paid in 2026 through 2035:

The expected benefits to be paid are based on the same assumptions used to measure our benefit obligation at December 31, 2025, and include estimated future employee service.

Other Employee Benefit Plans

401(k) Plan - The ONEOK 401(k) Plan covers all employees, and employee contributions are discretionary. We match 100% of employee 401(k) Plan contributions up to 6% of each participant’s eligible compensation, subject to certain conditions and limits. We also make profit-sharing contributions under our 401(k) Plan for employees who do not participate in our defined benefit pension plans. Effective January 1, 2025, quarterly profit-sharing contributions increased to 6% from 1% of each profit-sharing participant’s eligible compensation during the quarter. We may also make annual discretionary profit-sharing contributions of up to 2% of eligible compensation. Our contributions made to the plan, including profit-sharing contributions, were $128 million, $66 million and $44 million in 2025, 2024 and 2023, respectively.

EnLink terminated the EnLink 401(k) Plan effective January 30, 2025, prior to the closing of the EnLink Acquisition. Legacy EnLink employees were permitted to roll their EnLink 401(k) Plan account balance to the ONEOK 401(k) Plan, an individual retirement account or take a distribution. The EnLink 401(k) Plan was liquidated and closed in December 2025.

Medallion terminated the Medallion 401(k) Plan effective October 30, 2024, prior to the closing of the Medallion Acquisition on October 31, 2024. Legacy Medallion employees were permitted to roll their Medallion 401(k) Plan account balance to the ONEOK 401(k) Plan or an individual retirement account or take a distribution. The Medallion 401(k) Plan was liquidated and closed in September 2025.

Magellan terminated the Magellan 401(k) Plan effective September 24, 2023, prior to the closing of the Magellan Acquisition. Legacy Magellan employees were given the option to roll their Magellan 401(k) Plan account balance to the ONEOK 401(k) Plan or an individual retirement account or take a distribution. The Magellan 401(k) Plan was liquidated and closed in September 2024.

Nonqualified Deferred Compensation Plan - The 2020 Nonqualified Deferred Compensation Plan and its predecessor nonqualified deferred compensation plans (collectively, the NQDC Plan) provide a select group of management and highly compensated employees, as approved by our chief executive officer, with the option to defer portions of their compensation and receive notional employer contributions that generally are not available due to limitations on employer and employee contributions to qualified defined contribution plans under federal tax laws. Our investments which are included in other assets on the Consolidated Balance Sheets related to the NQDC Plan were not material. These investments are maintained in a rabbi trust. Our contributions to the plan were not material.