Sometimes a transaction looks clever on paper, but when you peek behind the curtain, nothing really changed except the tax bill. The tax system is not a game where form alone wins; courts have long had the power to ignore artificial labels and ask what actually happened in economic terms. At the same time, modern tax administration demands that taxpayers and advisors shine a light on aggressive positions, so the government can see what they are up to. In this chapter, we look at the common‑law anti‑abuse principles that courts use to collapse or disregard transactions, and the reporting rules that force disclosure of uncertain tax benefits and potentially abusive deals.