The question should in fact be: Who must NOT fill in a US Tax Retun?
as a US citizen must fill a tax form.
There are some instances when you may not be required to complete a federal income tax return. But more than 70% of those who fill in are due a refund, so it may be to your advantage to fill even if you are not required to.
The law does require you to complete a tax return if your income is above a certain level. Check the instructions for Form 1040, 1040A or 1040EZ
(under "filing requirements") for specific details that may affect your need to file a tax return with IRS this year (http://www.irs.gov/
In general, once you have the following gross income amounts, the law requires you to fill a federal tax return with the IRS:Single 7,800 USDHead of Household 10,050 USDMarried Filing Jointly 15,600 USDMarried Filling in Separately 3,050 USDGenerally, a person who is self-employed must file a tax return if his or her net earnings from self-employment for the year exceed 400 USD.
Even individuals who don't earn enough to be required to fill in a tax return may be eligible for an earned income credit up to 2,547 USD for a taxpayer with one qualifying child and 4,204 USD for a taxpayer with two or more qualifying children. Some individuals who do not have a qualifying child may be eligible for a credit of up to $382. However, you must fill in a return to receive the Earned Income Tax Credit. You must also fill in a return if you received any advance payments of this credit while you worked during the year.