Come 2014, you’ll have to pay a tax if you’re uninsured — but how exactly it’s going to work is still getting sorted out. The IRS isn’t sure how many people they’ll have to hire, or how much implementation will end up costing:

The changes will require new regulations, forms and publications, new computer programs and a big new outreach program to explain it all to taxpayers and tax professionals. Businesses that don’t claim an exemption will have to prove they offer health insurance to employees.

The health care law “includes the largest set of tax law changes in more than 20 years,” according to the Treasury inspector general who oversees the IRS. The agency will have to hire thousands of workers to manage it, requiring significant budget increases that already are being targeted by congressional Republicans determined to dismantle the president’s signature initiative.