Many tax planning strategies are imbedded in provisions of the tax law; however tax planners and tax preparers may push the limits of the law into gray areas such that positions taken on returns or in transactions have been challenged by the IRS. As a result, over time the courts have developed several judicial doctrines that have provided the IRS some power to challenge taxpayer positions taken in transactions and on returns filed. There are several judicial doctrines, name at least three and provide a brief explanation of the purpose of each doctrine.