On Thursday, nearly one million Americans will start receiving $500 checks from the Trump administration under its new Affordable Care Act refund program.

The payments are meant for a narrow group of people who bought their own health insurance through HealthCare.gov, the federally run ACA marketplace.

To be eligible, consumers must have enrolled in a HealthCare.gov plan and paid the full cost of their premiums without receiving federal premium tax credits or other financial assistance.

In a letter accompanying the checks, Trump said the refunds are for people who use HealthCare.gov, "but who do not receive Taxpayer Subsidies to help pay for their Coverage."

The program is also limited by geography. The payments are going to eligible consumers in the 30 states that use HealthCare.gov, rather than to those in state-run ACA marketplaces.

That means people who bought coverage through state-run exchanges are not eligible for the refund program.

States highlighted in blue below are eligible for the refunds:

Trump has framed the payments as refunds for what he says were excessive charges linked to the federal marketplace's operating costs.

Eligible people do not need to apply, submit a claim, or sign up for the program. Administration officials say they have already identified recipients and will mail the $500 checks automatically to their home addresses.

Each eligible enrollee will receive a separate payment. As a result, a household with multiple people who individually meet the requirements could receive more than one check.