A good explanation from Rick Ungar about how the GOP is trying to trick people with the whole tax-penalty thing:
In the opening paragraphs of Chief Justice Roberts’ opinion, he clarifies that the law specifically does not involve a tax. If it did, Roberts clarifies, the Court would have had no choice but to reject the case for lack of jurisdiction as a tax case cannot be brought until someone is actually forced to pay the tax. This is, as we know, not the case.
The fact that the Court found that the mandate was constitutional under the taxing authority granted Congress by the Constitution is an entirely different matter. This finding does not reduce the individual mandate to the status of a tax—it merely says that as the penalty for failing to purchase health insurance will fall to the Internal Revenue Service for collection, it was something Congress could provide for under its Constitutional authority.