The 1040 form is a standard tax form used by individuals in the United States to report their annual income to the Internal Revenue Service (IRS). It is essential for calculating the amount of tax owed or the refund due based on the taxpayer's income, deductions, and credits. There are several variations of the 1040 form, including the 1040-SR for seniors and the 1040-NR for non-residents. Taxpayers typically file the 1040 form by April 15 each year, although extensions may be available under certain circumstances.