Taxation is a governmental assessment upon property value, transactions, estates of the deceased, licenses granting a right and/or income, and duties on imports from foreign countries. It includes all contributions imposed by the government upon individuals for the service of the state. Taxes are usually divided into two main classes: direct and indirect. Generally speaking, direct taxes are those assessed against income, land or real property, and personal property, which are paid directly to the government; whereas indirect taxes are assessed against articles of consumption, such as products or services, but collected by an intermediary, such as a retailer. Tax Law is a complex system which encompasses the large body of laws governing taxation. It includes the payment of taxes to at least four different levels of government and many methods of taxation. Tax law is generated by the federal government, state government, as well as local government, which can include counties, cities, townships, districts, and other municipalities. It also includes regional entities such as school and utility, and transit districts. Tax law is extremely complicated and it changes every year. Its complexity and constant flux is generally due to two factors: the use of the tax code for purposes other than raising revenue, and the feedback process of amending the tax code. While the main intent of the tax law is to provide revenue for the government, the tax code is frequently used for public policy reasons i.e., to achieve social, economic, and political goals. The Federal tax law is administered primarily by the Internal Revenue Service, a bureau of the U.S. Treasury. The U.S. tax code is known as the Internal Revenue Code of 1986 as amended (Title 26 of the U.S. Code). Other federal tax laws are found in Title 26 of the Code of Federal Regulations; proposed regulations issued by the Internal Revenue Service (IRS); temporary regulations issued by the IRS; revenue rulings issued by the IRS; private letter rulings issued by the IRS; revenue procedures, policy statements, and technical information releases issued by the IRS; and federal tax court decisions. Tax law for state and local government is also contained in codes sections, regulations, administrative codes, procedures and statements issued by the respective government authorities, as well as state court decisions. The U.S. Tax Court is a federal agency with courts in major cities which decides controversies between taxpayers and the IRS involving underpayment of federal income, gift, and estate taxes. Tax Court hears these appeals de novo (as a trial rather than an appeal). Tax court decisions may be appealed to the Federal District Court of Appeals and are subject to the review of the U.S. Supreme Court. Tax attorneys can represent taxpayers in Tax Court and help them understand the complicated and confusing aspects of tax law. They represent taxpayers at all stages of tax controversies, including audit, IRS administrative appeals, trial and appellate court review.