Which form is primarily used to report individual income tax returns?

Form 1040 is the primary document that individual taxpayers use to report their income to the Internal Revenue Service (IRS) and calculate their tax liability for the year. It is specifically designed for individuals and sole proprietors to report their income, claim deductions, and credits, and determine any tax owed or refund due. The form is versatile and allows taxpayers to report various types of income such as wages, dividends, capital gains, and other sources.

In contrast, other forms mentioned serve different purposes: Form 1065 is used to report income, gains, losses, deductions, and credits from partnerships; Form W-2 is issued by employers to report wages, tips, and other compensation paid to employees, as well as the taxes withheld from these earnings; and Form 1099 is a series of forms used to report various types of income other than wages, salaries, and tips, primarily used for reporting income received by independent contractors and other non-employees. Therefore, while these other forms are integral to the income reporting process, they are not the primary vehicle for individual taxpayers to file their own returns.