Oops! How to Correct a Mistake on Your Filed Taxes

Alden Wicker

Sending off your completed tax return is an amazing feeling. Goodbye to all that work until next year!

That is, until you realize you’ve made a mistake.

Maybe an extra 1099 came in the mail. Or you read one of our many tax articles and found out you missed a huge credit that could save you a couple thou. Ummm, what next?

Mistakes happen. So the IRS has a special form just for you: the 1040X. It’s what you use to file an amended return.

Should I File an Amendment?

File an amendment if you:

Don’t file an amendment if:

  • You made a math error in adding or subtracting line items. The IRS will correct these for you.

What if you made a mistake that means you owe the IRS more in taxes, but the IRS didn’t notice? Can’t you just let it slide?

Bad idea. Besides the fact that this is tax fraud, if the IRS does discover this, you will have to pay the tax you owe plus interest that has accrued on it. It’s worth it to make sure you’re all buttoned up.

When You Can File an Amendment

If you filed before the deadline (which is usually April 15th), then you have three years from the deadline date.

how to fix mistake on tax formSo, let’s say that back when you filed taxes in 2010, you failed to claim a deduction for closing costs you incurred in 2009 (and you realized this after reading our post for homeowners). You can file an amended return to claim that deduction up until April 15th 2013, which is three years after the April 15th, 2010 filing deadline.

Let’s say you had a similar situation as above, but you couldn’t pay your taxes outright. You ended up paying the IRS in installments and finally paid off the last of your taxes in June 1, 2011. The IRS gives you more leeway here, giving you two years from when you paid off your taxes or three years from the filing date—whichever is longer—to file an amendment. So in this case, you can file an amendment up until June 1, 2013, which is two years after you finished paying for your 2009 taxes. (Find out what to do if you owe taxes and can’t pay.)

  • Emma

    this is really helpful! would I use the same 1040 and 1040X if I need to amend a K-1 I filed as an LLC? I filed the full 100% instead of my 51% portion. thanks!

    • laurashin

      Hi Emma,

      There isn’t an easy answer, so you should consult an enrolled agent or a CPA for the best advice on your personal situation.


  • Chris

    What if, as in your example, I paid $1000 in taxes, but then realized I missed deductions which could’ve lowered my taxes to $800? In other words, I overpaid $200 because of missed deductions. If I file a 1040X, will the IRS then just refund me the $200?

  • Sandy

    My son filed for 2012, but the return was rejected due to a name discrepancy with his youngest son versus the birth certificate. Means he is still waiting on the $$$, as well as his ex wife. He cannot of course find the letter from IRS, and hours on the phone has not helped. Would this form correct the problem?

  • vicki rivera

    I took out hardship withdrawals the last two years from my 401k the money I contribute is after tax my statement received from 401k for tax preparation said zero taxable amount yet h&r block added it to total income were they wrong?