Lawmakers have long used the tax code for purposes far beyond simply collecting revenue to fund the federal government. Through the insertion of specialized tax provisions, the tax code is used to achieve policy and political aims as well. But these special provisions come at a price: economic growth is foregone, higher accounting costs are incurred, more lobbyists are hired to protect tax advantages, and revenue is lost as a result of collection inefficiencies. We estimate that hidden costs of tax compliance range from $215 billion to $987 billion annually, and that part of the $452 billion revenue gap in 2012 unreported taxes was the result of tax code complexity. We provide policy recommendations based on lessons from the Russia flat tax reforms and the Tax Reform Act of 1986.