The 1040 (10-40) form, along with its supplemental schedules, is the most complex federal income tax form. Generally, taxpayers with complicated tax situations or those claiming several deductions, tax credits, and adjustments to income should use this form when filing.

A simpler version of the 1040 federal income tax form is the 1040A form. Individuals who choose to file with this form usually have a taxable income of less than $100,000 and receive income only from wages, salaries, tips, ordinary dividends, retirement plans, and interest income.

Form 1040EZ (10-40-E-Z) is the easiest and quickest income tax form to file. However, only taxpayers who meet specific income limits and fulfill certain filing requirements can use this form.

The three forms you can use for filing your individual federal income tax returns are Form 1040EZ (10-40-E-Z), 1040A (10-40-A), and 1040 (10-40). Form 1040EZ is the simplest form to fill out, but you must meet certain conditions to use it.