The Federal Tax Law is the set of U.S. federal government rules that make up the complete tax code requirements on a federal level. The entire tax code runs in the tens of thousands and can be updated frequently. They do not stand alone in terms of taxation, as the state level also has a tax law and all tax laws are mandatory for U.S. citizens and people working in the U.S. under all visa systems.
The tax code is for businesses as well as personal filing, and outlines the percentage that is expected to be paid in tax relating to every transaction such as taxes relating to employment and taxes relating to the sale of land or other personal property. Taxes are usually sliding in the sense that there is a different rate of tax depending on the bracket (the overall value) of the service performed or merchandise bought.