"Nothing in the new guidance regarding employer reporting and responsibility will limit individuals' eligibility for premium tax credits to buy insurance through the marketplaces that open on Oct. 1," she said.
Under the law, most Americans will be required to have insurance in January 2014, or they will be subject to tax penalties. The announcement on Tuesday did not say anything about delaying that requirement or those penalties.
Administration officials sought to put the action in a positive light in the online announcements, and they emphasized that the existing insurance coverage of most Americans would not be affected.
"We have heard concerns about the complexity of the requirements and the need for more time to implement them effectively," Mark J. Mazur, an assistant Treasury secretary, wrote on the department's Web site. "We recognize that the vast majority of businesses that will need to do this reporting already provide health insurance to their workers, and we want to make sure it is easy for others to do so."
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The 2010 Affordable Care Act required employers with more than 50 full-time workers to offer them affordable health insurance starting next year or face fines. Some companies with payrolls just above that threshold said they would cut jobs or switch some full-time workers to part-time employment so that they could avoid providing coverage.
Under the provision to set up state-based marketplaces, subsidies are supposed to be available to many lower- and middle-income people who do not have access to coverage from employers or other sources. It may be difficult, however, for officials running the exchanges to know who is entitled to subsidies if employers do not report information on the coverage they provide to workers.
Enrollment in the exchanges is to begin Oct. 1, with insurance coverage taking effect on Jan. 1. "We are on target to open the health insurance marketplace on Oct. 1 where small businesses and ordinary Americans will be able to go to one place to learn about their coverage options and make side-by-side comparisons of each plan's price and benefits before they make their decision," Valerie Jarrett, Mr. Obama's senior adviser and liaison to the business community, wrote on the White House Web site.
But even some supporters of the law dispute that the establishment of the health insurance exchanges is on schedule, especially since progress varies by state and some Republican-led states are resisting the health care law and withholding resources for putting it into effect.
Much of the administration's public effort, especially at the Department of Health and Human Services, has been directed toward spreading the word to uninsured Americans, especially younger and healthy individuals whose participation is needed to help keep down premiums for everyone else. About 85 percent of Americans are insured, so most individuals will be unaffected, at least initially.
Behind the scenes, however, the administration has been fielding questions and criticisms from businesses about the reporting requirements — especially the Treasury Department, which has responsibility, given its oversight of the tax reporting system.
(Read More: WillObamacare Hurt Jobs? It's Already Happening)