In July 2013, the administration deferred that requirement until 2015. Seven months later, the administration announced a further delay, until 2016, for employers with 50 to 99 employees.

The suit accuses the Obama administration of unlawfully postponing a requirement that larger employers offer health coverage to their full-time employees or pay penalties. (Larger companies are defined as those with 50 or more employees.)

The lawsuit — filed against the secretaries of the Health and Human Services and Treasury Departments — focuses on two crucial aspects of the way the administration has put the Affordable Care Act into effect.

House Republicans filed a long-threatened lawsuit Friday against the Obama administration over unilateral actions on the health care law that they say are abuses of the president's executive authority.

The suit also challenges what it says is President Obama's unlawful giveaway of roughly $175 billion to insurance companies under the law. According to the Congressional Budget Office, the administration will pay that amount to the companies over the next 10 years, though the funds have not been appropriated by Congress. The lawsuit argues that it is an unlawful transfer of funds.



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That issue involves subsidies known as cost-sharing reductions, which the federal government pays to insurers on behalf of people whose incomes range from the poverty threshold to two and a half times the poverty threshold ($11,670 to $29,175 a year for an individual). If the lawsuit is successful, poor people would not lose their health care, because the insurance companies would still be required to provide coverage — but without the help of the government subsidy, the companies might be forced to raise costs elsewhere.



The subsidies reduce the co-payments, deductibles and other out-of-pocket costs that consumers incur when they go to doctors and hospitals.



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The lawsuit came a day after Mr. Obama outlined his plan to unilaterally move forward on an immigration overhaul, allowing as many as five million undocumented immigrants to live and work in the United States without threat of deportation. House Republicans call it "executive amnesty" and had threatened either to add an immigration component to the lawsuit filed on Friday, which addresses only the Affordable Care Act, or began a separate legal action.



"Time after time, the president has chosen to ignore the will of the American people and rewrite federal law on his own without a vote of Congress," Speaker John A. Boehner said in a statement. "If this president can get away with making his own laws, future presidents will have the ability to as well. The House has an obligation to stand up for the Constitution, and that is exactly why we are pursuing this course of action."



Democrats have cast a legal challenge as strange. Republicans, they say, are attacking Mr. Obama for delaying enforcement of a law that they vehemently oppose. The health care law was passed in 2010 without any Republican votes, and House Republicans have voted dozens of times to repeal all or part of it.



Mr. Boehner has been talking about suing the president since the summer, and in July, House Republicans passed a resolution authorizing the House to legally challenge Mr. Obama over the use of his executive authority to change parts of the health care law.



House Republicans struggled to find a law firm willing to take their case. Two withdrew, but on Tuesday, Mr. Boehner hired Jonathan Turley, a professor at George Washington University.