If you qualify, you may opt to have the IRS figure your tax and certain credits on Form 1040 (PDF). This option is available even if you're not required to file a tax return but would like to request a refund of taxes paid or would like to claim certain tax credits, such as the earned income credit or the tax credit for the elderly or the disabled. For more information on having the IRS figure your tax and credits, including information you should provide to the IRS and circumstances in which the IRS won't figure your tax, refer to Chapter 29 of Publication 17, Your Federal Income Tax for Individuals.
After the IRS figures your tax, you'll either receive a refund if you overpaid your tax or a bill if you underpaid your tax. If you receive a bill, you can avoid interest and late-payment penalties if you pay the amount due within 30 days of the date of the bill or before the due date of the return, whichever is later. Note that you may be charged a penalty for underpayment of estimated tax if applicable. Refer to Topic No. 306, Penalty for Underpayment of Estimated Tax for more information.