If you experienced an income reduction that makes you newly eligible for premium tax credits and had minimum essential coverage for at least one day during the 60 days prior to your income change, in most states, you qualify for a special enrollment period as long as you apply within 60 days of your change in status (there may be an extension for exceptional circumstances).
If you are currently enrolled in marketplace coverage and experience an income change that impacts your eligibility for premium tax credits, you should be able to access a special enrollment period in every state. In general, you can only change plans with this SEP within the same metal level as your current plan.
If you are currently or were recently enrolled in an individual market plan outside of the marketplace and have had a loss of income that makes you newly eligible for premium tax credits, you should contact the marketplace in your state to determine if you are eligible for a SEP – in many states, you might have to apply through the marketplace call center. (45 C.F.R. § 155.420; 82 Fed. Reg. 18346, April 18, 2017; CMS, Federally Facilitated Exchanges (FFEs) and Federally Facilitated Small Business Health Options Program (FF-SHOP) Enrollment Manual, September 2, 2020).