The Rural Hospital Emergency Room Guarantee Act establishes a dedicated "Rural Hospital Emergency Room Guarantee Fund" within the U.S. Treasury, administered by the Secretary of Health and Human Services through the Health Resources and Services Administration. This fund is designed to provide a guaranteed funding stream to keep existing emergency rooms at America's rural hospitals open, ensuring access to critical care in underserved areas. The bill mandates a 10-year program to make payments to eligible rural health facilities that operate 24-hour emergency departments and participate in federal healthcare programs. Initial annual payments are set at $1,000,000, distributed quarterly, and adjusted annually for inflation based on the Consumer Price Index for Medical Care Services. Additionally, eligible entities may receive an extra payment of up to 50 percent of the initial amount, determined by factors such as payor mix, patient injury needs, local economic conditions, and financial history. The program also includes provisions for emergency payments of up to $250,000 if an eligible emergency department is at risk of closing within 14 days. Funds received can only be used for the normal operating expenses and staffing of the emergency department, explicitly prohibiting use for executive compensation, new projects, or transfers to other facilities. A key condition of participation is that eligible entities cannot be acquired by private-equity, venture-capital, or similarly purposed ownership funds. To ensure accountability, participating entities must submit annual financial reports, though this information cannot be used for disqualification from the program. The Secretary is also required to conduct random audits to ensure compliance, with violations potentially leading to civil penalties or removal from the program. The fund is supported by mandatory appropriations from the Treasury for fiscal years 2026 through 2036, and participation does not affect eligibility for other federal healthcare programs.