No one is forced to change plans due to a change in eligibility for Affordable Care Act subsidies. However, if you are enrolled in a marketplace plan, your annual household income changed, and you now earn more than 250 percent of the federal poverty level (which is the income limit to qualify for cost-sharing reduction subsidies, or CSRs), you are entitled to a special enrollment period, but prior to January 2022, you can only enroll into a plan within the same metal level as your current marketplace plan.
Prior to January 2022, if your annual household income no longer qualifies you for cost-sharing reductions, the insurer is required to change your plan to the correct standard silver plan or plan variation once your insurer is notified by the marketplace about such a change in eligibility. Because you’ll continue to be enrolled in a silver plan (but with different cost-sharing, appropriate to your income), then out-of-pocket costs already paid during that year must be counted against the out-of-pocket costs required under the new version of the plan.
Beginning in January 2022, silver plan enrollees who lose eligibility for CSRs may change to a plan one metal level above or below their current plan, but they are not required to do so.
(45 C.F.R. § 155.420(a)(4)(ii)(B)).