Tax Guide Form 1040x: What if You’ve Made a Mistake on Your Tax Form? This post was updated in April 2018 Form 1040x: Amended U.S. Individual Income Tax Return With all the tax filing that you have to do by a particular due ... Tax Guide Form 1040X: A Second Chance to Get Your Return Right IRS Form 1040X – the Amended U.S. Individual Income Tax Return PDFfiller focuses on one more form related to the individual tax return, Form 1040x, which lets you amend ...