The basic form that is used by taxpayers to file their income tax returns. The form is on one double-sided piece of paper. Schedules may be attached to the form. For example, if mortgage interest, medical, and other expenses are itemized and deducted from income, Schedule A is attached to Form 1040. Business expenses for unincorporated business owners are included on Schedule C. Individuals who make a modest amount of money and have uncomplicated tax situations can use Form 1040 EZ.