Today's Supreme Court arguments on the Affordable Care Act centered around whether or not the penalty for failure to obtain health insurance is a tax, and if it is a tax, whether the parties have standing to sue over it before it has been assessed. The full transcript is here (PDF).
Since the requirement to obtain health insurance is not effective until 2014, the earliest date anyone would be paying a penalty for not obtaining it would be sometime in 2015.
There are two prongs to the argument for why the AIA would apply: First, if it did not apply to the penalties, that opens the gate for every other tax penalty to be litigated before it's assessed. Second, Congress specified that the penalty should be assessed and collected in the same manner as a tax, even though it's a penalty.
The justices actively questioned Robert Long, the attorney appointed to argue that the Anti-Injunction Act (AIA) applies in this case. His argument centered around the idea that the penalty in the Affordable Care Act is paid via tax return, and the AIA applies to tax penalties and taxes alike. He pointed out that Congress directed that the penalty should be assessed and collected in the same manner as taxes, that the penalties were included in taxes, and that the penalty has the same properties as a tax because the statute says the penalty "shall be assessed and collected in the same manner as taxes."
Legal arguments aside for a moment, I found some humor in this comment by Justice Scalia:
If it's not jurisdictional, what's going to happen is you are going to have an intelligent federal court deciding whether you are going to make an exception. And there will be no parade of horribles because all federal courts are intelligent.
This post from SCOTUSblog summarizes Mr. Long's entire argument: