Amend Your Tax Return to Correct a Filing Mistake
I realize I made a mistake on my 2015 taxes. Is it too late to fix it?
You generally have up to three years from the due date of the original return to file an amended return. Use IRS Form 1040X to note the changes you're making, and include revised copies of any supplemental forms that are affected (such as Schedule A for changes to itemized deductions).
You cannot e-file an amended return. Amended returns take up to 16 weeks to process, so if you owe additional taxes, pay as soon as possible to avoid interest and penalty charges. If the change you've made lowers your tax bill, the IRS will send you a refund.