What form is used to calculate federal income tax?

The primary form used to calculate federal income tax for individuals is the IRS Form 1040. Taxpayers report their income, deductions, and credits on this form to determine their tax liability or refund. There are also simplified versions, such as Form 1040-SR for seniors and Form 1040-EZ for those with straightforward tax situations, though the latter has been phased out in recent years. Additional schedules may be required for specific income types or tax credits.