WASHINGTON – The Supreme Court's decision to uphold most of President Barack Obama's health care law will come home to roost for most taxpayers in about 2½ years, when they'll have to start providing proof on their tax returns that they have health insurance.

That scenario puts the Internal Revenue Service at the center of the debate, renewing questions about whether the agency is capable of policing the health care decisions of millions of people in the United States while also collecting the taxes needed to run the federal government.

Under the law, the IRS will provide tax breaks and incentives to help pay for health insurance and impose penalties on some people who don't buy coverage and on some businesses that don't offer it to employees.