The Obama administration took new steps Wednesday toward implementing the individual mandate in its signature healthcare law, downplaying the scope of the unpopular provision by stressing rules that allow exemptions from the requirement to purchase insurance.

The Internal Revenue Service and the Health and Human Services Department emphasized exceptions to the mandate, which were detailed in new regulations that also laid out the process by which the IRS will calculate penalties for going uninsured.

The mandate requires most taxpayers to either buy insurance or pay a fine to the IRS. It’s one of the most politically unpopular provisions of the healthcare law, and was at the core of last year’s historic Supreme Court case over the healthcare law.

HHS referred to the politically charged provision as a system of “shared responsibility” payments.