If you filed your taxes, but now need to make changes, you can file an amended return, using Form 1040-X, Amended U.S. Individual Income Tax Return. You should amend your return if you reported certain items incorrectly on the original return, such as filing status, dependents, total income, deductions, or credits. The IRS notes that you don’t usually have to amend a return because of math errors that were made, because the IRS usually corrects them. They also note that you won’t typically need to file an amended return because you forgot to include forms, such as W-2s or schedules, when you filed. The IRS will normally request those forms from you. A tax professional can help guide you through the right next steps and can help you avoid needing to submit an amendment in the future.