If you've already filed a tax return but need to make a change, you may file an amended return. This goes for income you may have forgotten, deductions you didn't take, or tax credits that you didn't know about. The Internal Revenue Service allows amended returns but also imposes conditions and time limits.
Forms and Corrections
You use a printed Form 1040X to file an amended tax return. The form gives information on your previous return and your calculation of the corrected tax amount. You must include schedules and forms that document your corrections. You may correct any information on the return that affects the amount of your tax liability. If you have not claimed a dependent that was eligible, you may add that dependent and reduce your taxable income. In addition, you may claim a child tax credit that you may have miscalculated, or forgot about altogether. Claiming new deductions, exemptions and credits will lessen your taxes.
If you have found calculation errors on the return you already filed, but otherwise filled out the form correctly, you don’t need to file an amended return. The IRS processes the returns and checks the math, and will know when an error in calculation has taken place. Nevertheless, if the agency attempts to correct your calculations, double-check your numbers very thoroughly before responding.
The IRS will process the amended return and adjust your tax liability in the year for which you filed that return. It can take several months for the agency to review the return and make the adjustment. This may result in an additional tax refund to you, or a tax bill if you owe more tax than was paid.
The statute of limitations on amended tax returns is three years. This is the period set by law that permits the IRS to issue tax refunds. The three-year period begins on April 15, the deadline for filing tax returns for the previous year. If you requested an extension of time to file your return, the three-year limit is counted from Oct. 15 (no matter when you actually filed). If you owe tax with an amended return, you have until April 15 of the following year to pay it without penalty or interest.
There is no statute of limitations if you are filing an amended return that results in a higher tax liability -- for example, if you did not report income, or if you took a deduction that was not allowed. If you have missed the three-year deadline and believe you paid too much, you can still file an amended return, but the IRS will only refund money that was paid over the two years before the amended return is filed.