As a result, some families that can't afford the employer coverage that they are offered on the job will not be able to get financial assistance from the government to buy private health insurance on their own. How many people will be affected is unclear.
The Obama administration says its hands were tied by the way Congress wrote the law. Officials said the administration tried to mitigate the impact. Families that can't get coverage because of the glitch will not face a tax penalty for remaining uninsured, the IRS rules said.
"This is a very significant problem, and we have urged that it be fixed," said Ron Pollack, executive director of Families USA, an advocacy group that supported the overhaul from its early days. "It is clear that the only way this can be fixed is through legislation and not the regulatory process."
But there's not much hope for an immediate fix from Congress, since the House is controlled by Republicans who would still like to see the whole law repealed.
The affordability glitch is one of a series of problems coming into sharper focus as the law moves to full implementation.
Starting Oct. 1, many middle-class uninsured will be able to sign up for government-subsidized private coverage through new health care marketplaces known as exchanges. Coverage will be effective Jan. 1. Low-income people will be steered to expanded safety-net programs. At the same time, virtually all Americans will be required to carry health insurance, either through an employer, a government program, or by buying their own plan.
Bruce Lesley, president of First Focus, an advocacy group for children, cited estimates that close to 500,000 children could remain uninsured because of the glitch. "The children's community is disappointed by the administration's decision to deny access to coverage for children based on a bogus definition of affordability," Lesley said in a statement.
The problem seems to be the way the law defined affordable.
Congress went on to say that what counts as affordable is keyed to the cost of self-only coverage offered to an individual worker, not his or her family. A typical workplace plan costs about $5,600 for an individual worker. But the cost of family coverage is nearly three times higher, about $15,700, according to the Kaiser Family Foundation.
So if the employer isn't willing to chip in for family premiums – as most big companies already do – some families will be out of luck. They may not be able to afford the full premium on their own, and they'd be locked out of the subsidies in the health care overhaul law.
Employers are relieved that the Obama administration didn't try to put the cost of providing family coverage on them.
"They are bound by the law and cannot extend further than what the law provides," said Neil Trautwein, a vice president of the National Retail Federation.