Consumers who have unresolved discrepancies over their incomes will get notices at a later date.
The new health law provides subsidized coverage to people with no access to health insurance on the job. More than 80 percent of those signed up are getting subsidies to help with their premiums and, in some cases, their copays and deductibles as well.
But those taxpayer subsidies are contingent on meeting a host of requirements. The amount of a consumer's premium tax credit can vary by income, family size, hometown and other factors. That can make getting covered through the law feel somewhat like doing your taxes.
The letters that started going out Tuesday won't be the final attempt to reach those with unresolved issues. HHS will try to contact each consumer two more times by phone and once via email. The administration is also working with local organizations to try to reach people directly in their homes.
Consumers can also contact HealthCare.gov's call center at 1-800-318-2596 to see what documents they need to submit and see whether their information has been received.
The notices affect this year's coverage only.
The open enrollment period for this year is over. Open enrollment season for 2015 coverage doesn't start until Nov. 15. At that point, consumers will be able to renew or make changes in their coverage, and new customers can find out whether there's a plan that's right for them.
Under the law, most Americans are required to have health insurance or risk fines.