When you amend a federal tax return, you can correct mistakes or errors made on your original one. Here’s what you need to know about the process, including when to file, what documents you’ll need, and what timeline to expect.

An amended tax return, known as Form 1040-X, Amended U.S. Individual Income Tax Return, is an IRS document for updating information on your original tax return.

You can access Form 1040-X directly on the IRS website or by using an online tax software, like H&R Block, TaxAct, or TurboTax.

Not every error requires filing a 1040-X. The IRS generally corrects minor mathematical mistakes without requiring an amended return.

You also don’t need a 1040-X if the IRS asks for additional documents after accepting your original return.

However, you may need to amend a return if, after filing your original one, you have changes to the following:

• Filing status

• Dependents

• Income

• Credits or deductions

If you’re unsure whether you should file, you can use the IRS Should I File an Amended Return tool to help you decide.

Follow these steps to amend your tax return. You can file on your own or choose the help of a tax professional.

To start, grab your original tax return that needs the changes. You can file up to three amended returns electronically in a given tax year.

You’ll also need to collect supporting information that verifies the changes you’re making.

For example, if you need to update your wages, you’ll likely have a new or amended W-2. Or, if adding a dependent, make sure you have their Social Security number.

Even changes to deductions or credits will require documentation — such as Form 1098-E to claim the student loan interest deduction.

In addition to Form 1040-X, you may be required to fill out other IRS forms. For example, you’ll need to complete Schedule A for changes to your itemized deductions or Schedule E for supplemental income, such as from a rental property.

You’ll submit any additional tax forms with your 1040-X.

The 1040-X has many similarities to Form 1040, the form you filed for the original return. However, there are major differences to note.

Columns A through C will highlight your changes. Column A is the original number, column B notes the amount of the change, and column C is for the new amount.

In part II of Form 1040-X, you’re required to explain why you’re making changes to your tax return — for example, you forgot to claim a credit or received a new W-2.

You can generally file an amended return within three years of filing your original one — or, if you owed money, two years after the date you paid the tax, whichever is later.

There are special situations where the IRS may allow an extension, such as if you’re in an area federally declared a disaster, a combat zone, or if you’re claiming bad debt or worthless security.

Once you’ve filed your amended tax return, there are a few steps to take to ensure a smoother process.

• Review your state tax return: If you need to amend it, that’s a separate process. Check your state’s website for how to file.

• Check your amended tax return status: You can check the status of your return three to four weeks after filing. However, it could take 8 to 12 weeks for the IRS to process your 1040-X, longer if there are errors or missing information.

• Prepare for a potential payment or refund: If you owe additional taxes after amending your return, you’ll need to pay by the traditional tax deadline, April 15. Refunds for tax years after 2021 can be requested by direct deposit if you filed electronically.

If it’s been more than 16 weeks since you filed your amended return, and you haven’t heard anything, you can contact the IRS by calling 800-829-1040.

Yes, you can complete Form 1040-X and any required additional tax forms and file them electronically or by mail. You can access all forms on the IRS website or use an online tax software.

While there’s no penalty for filing an amended return, the IRS may charge fees for late tax payments, erroneous claims, or frivolous returns.

You can check the status of your amended tax return three to four weeks after filing, using the IRS Where’s My Amended Return tool. It can take 8 to 12 weeks for the IRS to process your return, longer if it’s returned for more information, is incomplete, or needs special review.