The Budget Reconciliation Act of 2025, also known as the One Big Beautiful Bill Act (OBBBA), made major changes to both Medicaid and the health insurance Marketplaces. In this paper, we focus on one of the Medicaid provisions: by December 31, 2026, states must start redetermining eligibility for Affordable Care Act (ACA) Medicaid expansion enrollees every six months. This eliminates a provision of the ACA under which eligibility for Medicaid expansion enrollees is redetermined once every 12 months.

Why This Matters

This provision will result in lower Medicaid expansion enrollment, as people lose Medicaid either because they are procedurally disenrolled (losing coverage because of administrative issues without their eligibility being determined) or found ineligible in the new redeterminations. The incomes of low-income working people are more likely to change notably during the year than those of higher-income workers, so this provision will result in many low-income workers having their coverage disrupted repeatedly over time as their income fluctuates around the Medicaid eligibility threshold. Disruptions in coverage for Medicaid expansion enrollees because of six-month redetermination can result in worse health, delays in obtaining health care, unmet health needs, financial insecurity, and increased barriers to employment.

What We Found

Our main findings are the following:

• Medicaid expansion enrollment in an average month of 2028 would be 18.2 million if 12-month eligibility redetermination remained in place. We estimate that 77 percent of Medicaid expansion enrollees facing their six-month redetermination would keep their coverage, 13 percent would be found no longer eligible because of higher earnings that month, and the remaining 11 percent would be procedurally disenrolled if procedural disenrollment rates in 2028 remain consistent with evidence from 2025. However, some of those people who are disenrolled may regain eligibility and re-enroll. Under this scenario, average monthly Medicaid expansion enrollment will be reduced by 3.1 million, or 17.0 percent.
• If all states matched the procedural disenrollment performance of the states with best practices, we estimate that 81 percent of enrollees facing their six-month redetermination would maintain their coverage, 12 percent would be found no longer eligible, and the remaining 7 percent would be procedurally disenrolled. Again, some of those disenrolled would re-enroll later in the year. Under this best-case scenario, average monthly enrollment would be reduced by 2.0 million, or 10.7 percent.

How We Did It

For this analysis, we used the Urban Institute’s Health Insurance Policy Simulation Model and analysis of data from the Survey of Income and Program Participation to estimate changes in Medicaid enrollment and health coverage under six-month redetermination for Medicaid expansion enrollees.