Internal Revenue Code - IRC
  
The Internal Revenue Code is the whole mass and mess of laws that affect excise taxes, income taxes, and transfer taxes in the U.S.
What's deductible? What are the price breaks when federal tax rates go from 15% to 20% to...worse? If you're late with a payment, what are the fines? What is "due process" when it's discovered that you likely defrauded the government on taxes you owe?
Stuff like that. Endless laws for endless streams of dough back to our gov, in return for, um, managing us like a semi-detached parent.