The goal of the 2010 Affordable Care Act is to provide access to health coverage for the nation’s estimated 48 million uninsured. Major provisions took effect Jan. 1, including the sale of health plans through new government insurance marketplaces. More than 4.2 million Americans have enrolled in private health insurance through the exchanges, the administration said this week.

No provision of the law is more controversial than the individual mandate, a concept that even Obama didn’t support until after he was elected president. Health insurers have said that to remain financially viable while offering coverage to everyone, regardless of whether they are sick as the law maintains, the government also must require all Americans to obtain insurance. The theory is that premiums from young and healthy people who don’t need much medical care can balance the risk and cost of caring for those who are older or unhealthy.

Concerns Raised

“We have consistently raised concerns about any effort to sever the link between insurance market reforms and the individual mandate,” Robert Zirkelbach, a spokesman for America’s Health Insurance Plans, the industry’s Washington lobby group, said in an e-mail.

Most Americans don’t have to worry about the law’s mandate because they’re covered by health plans offered by employers or government programs, including Medicare and Medicaid. Only about 5 percent of the population bought insurance for themselves in 2012, according to the Kaiser Family Foundation, a Menlo Park, California-based nonprofit group that studies health-care issues.

With just weeks until the March 31 enrollment deadline for 2014, the Obama administration has begun warning Americans that a penalty will apply if they don’t carry insurance starting April 1. The government publicly released the form Americans must use to apply for an exemption late on Dec. 19, as part of regulatory guidance. It wasn’t accompanied by a news release.

‘Hardship’ Cases

“The Affordable Care Act requires people who can afford insurance to buy it, so that their medical bills are not passed onto the rest of us, which drives up health-care costs for everyone,” Joanne Peters, a spokeswoman for the Health and Human Services Department, said in an e-mail. The form “allows a limited number of individuals who are facing hardship to apply for an exception. This exception also makes it easier to find insurance by allowing those individuals to access catastrophic- level plans.”

Before enrollment began in October, administration officials had said they hoped to meet a Congressional Budget Office enrollment target of 7 million people in private plans in 2014. The CBO revised that estimate to 6 million in February.

There are 14 categories of exemptions, including one covering low-income people who have been denied Medicaid coverage in the 25 states that have declined to expand that program under the health-care law. That population alone may number about 5 million, according to the Kaiser foundation.