Generally, most income you receive is taxable. But there are some situations when certain types of income are partially taxed or not taxed at all. A complete list is available in IRS Publication 525, Taxable and Nontaxable Income.
The Free File program is a free (U.S.) federal tax preparation and electronic filing program for eligible taxpayers developed through a partnership between the Internal Revenue Service (IRS) and the Free File Alliance LLC, a group of private sector tax software companies. . .
You must file a tax return if your income is above a certain level. The amount varies depending on filing status, age and the type of income you receive.