This chapter examines the rise of the Independent Fiscal Institution (IFI) within the institutional structures of modern states. A new feature of the regulatory landscape in most of the jurisdictions where they are to be found, these institutions are designed to encourage fiscal responsibility on the government’s exercise of its budgetary responsibilities. The IFI often forms part of post-Global Financial Crisis (GFC) regulatory architecture1 and is familiar to students of political economy and financial regulation. But even though their activities relate directly to government in a way that is less true of other post-GFC innovations, IFIs have been largely ignored in the specialist public law literature, a by-product of the tendency among public lawyers to overlook the political economy dimensions of their field.2