The Trump administration began sending $500 payments to about 950,000 people enrolled through the federal Affordable Care Act marketplace, according to the White House and Reuters. The checks are accompanied by a letter signed by President Donald Trump.

Eligibility is limited to people in the 30 states that use HealthCare.gov who paid full-price premiums without federal premium assistance. Residents of the 20 states that operate their own marketplaces are excluded. The White House announced the refunds on Sept. 10 and said checks would begin going out in October.

The administration describes the money as a refund of exchange user fees that it says were collected in excess of HealthCare.gov’s operating needs under the Biden administration. That characterization is the White House’s. The recipients are not representative of all ACA enrollees, most of whom receive subsidized coverage.

The payments arrive about a month before the Nov. 3 midterm elections. Reuters calculated that 71% of the money—$339 million—will go to residents of 13 states with prominent Senate or gubernatorial contests. Critics argue the timing is political, while the White House says it is returning money that belongs to consumers.