Amending Your State Tax Return
Complete and submit a Form 1040X to the Internal Revenue Service. If you filed your taxes yourself or used an online service, you can obtain a 1040X from the IRS website. Mail the completed form to the IRS with payment of any taxes that are due.
Contact your state's Department of Revenue to obtain the correct form to amend your state tax return. The federal IRS website provides a link to each state's Department of Revenue. This link allows you to obtain the form you need. The amendment forms vary for each state, but many states use the letter "X" in their amendment forms, according to TurboTax.
Complete the state amendment form and submit it to your state's Department of Revenue. The form should have the correct income, deductions and filing status that should have gone on the original tax return. If the amendment results in additional taxes due, mail the tax payment with the amendment to the Department of Revenue. Provide a copy of the 1040X, federal amendment of your tax return, with the state amendment.