If you are wondering which of the federal tax forms you should use to file taxes this year, ask yourself a few questions. Is my taxable income $100,000 or more? Will I be itemizing my deductions? Will I be claiming any dependents? Will I be reporting self-employment income? If you answer, “Yes,” to one or more of these questions, chances are you need to use IRS Form 1040 to file your taxes. For more detail on which tax form to use, visit IRS.gov and read Publication 17, Your Federal Income Tax. It's loaded with guidance on all of the three federal tax forms as well as tons of other tax tips.