What if I Gave the Wrong Mileage on My Tax Return by Accident?

When you report the wrong mileage on your income tax return, the amount of your refund or tax bill is inaccurate. Claiming too much mileage will decrease the tax you owe, while claiming too little mileage will increase your owed tax. To fix an error after you file your initial income tax return, file an amended return.

Form 1040X, or the Amended U.S. Individual Income Tax Return, allows you to correct any mistake you make on your income tax return. Although you can complete the return as soon as you realize the mistake, the IRS asks that you wait to submit the amended return until your return is processed or you receive your refund, whichever is first. Unlike with filing a regular return, the IRS does not accept amended returns electronically – only through standard mail.

If you are a small-business owner or an independent contractor, you must amend your return using Form 1040X and Schedule C. Report the correct mileage on Schedule C and enter your modified adjusted gross income on Form 1040X. Attach Schedule C to your amended return. Because the IRS determines your tax bill according to your AGI, any changes to this amount will reflect on your tax liability.

If you’re an employee who receives a W-2 at the end of the tax year, claiming work-related mileage requires you to itemize your deductions, which must exceed your standard deduction to be worthwhile. If you are claiming less mileage, make sure that the amount of your itemized deductions continues to exceed your standard deduction. If it does not, claiming the standard deduction might be more financially beneficial for you. To claim mileage and itemize deductions on an amended tax return, you must complete a new Schedule A and Form 2106 to make the adjustment. Enter the new itemized deduction amount on Form 1040X and attach the supporting forms to your return.