Form 1040X Instructions – How to File an Amended Tax Return

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1040x tax formIf you spent days poring over your tax return this year and mailed it in by the tax filing deadline, only to discover that you forgot to claim the computer that you bought as a work deduction, don’t fret. You can still claim this deduction, as well as fix any other errors you may have made.

Essentially, the IRS allows you a “do-over” on your taxes. You can fix any mistakes after your initial tax filing, by utilizing Form 1040X. And you may have more time to do so than you think.

What Is the 1040X?

The 1040X is a tax form that lets you amend or change your return up to three years after you filed the original return.¬†You can use 1040X to correct any of the 1040 tax forms. If you made a mistake on another form, such as a Schedule A, you simply have to redo that form and include a new copy when you file the 1040X. The important thing is to determine how the changes to any other form would affect your 1040 – that’s what you input on the 1040X.

The 1040X is much simpler now than in the past. Previously, you had to go over every line of the 1040 and determine whether any changes needed to be made. Now, the IRS has significantly simplified the 1040X by boiling it down to its core components: your total income, how much your tax liability has changed, payments you’ve made, and any refunds you’re now due or payments that you now need to make. There is a lengthier section on exemptions, generally because you need to provide a good reason as to why you couldn’t accurately determine your number of dependents the time you filed, so that part is more in-depth. But otherwise, the form is simple to complete.

There is one downside: If you’re owed more money due to your changes, you might not get it as quickly as you hoped. Every 1040X is reviewed by a person, so it can take up to three months to process.

How to Complete Form 1040X

Each line on the form requires that you input a values into three columns:

  • Column A: The original value as it appears on your original tax return (or, if you’ve already amended it, from your last 1040X)
  • Column B: The amount that the value has increased or reduced due to your changes
  • Column C: The actual corrected value

Unless you’re making multiple changes, most of the values in Column A will simply be copied over to Column C, yielding a change of zero.

1040x tax form

Let’s look at each section on the 1040X individually:

Filing Status

You can change your filing status by filing an amended return. You cannot change from filing as married filing jointly to married filing separately after you’ve already filed your taxes, but you can change any other status.

Income and Deductions

1. Adjusted gross income: Add or subtract any income or deductions that you need to change, and then you can retrieve your adjusted gross income from line 37 of the 1040.

2. Itemized deductions or standard deductions: Determine any changes that have occurred and input the new number.

3. Subtract your itemized or standard deduction from your adjusted gross income.

4. Exemptions: If you’re changing any exemptions, you’ll need to complete Part 1 of the form (on the second page) to explain your position precisely.

5. Subtract your total exemption amount (line 4) from your adjusted gross income (line 3) and you have your taxable income.

Tax Liability

6. Tax and method used to figure tax: It is recommended that you use the tax tables.

7. Credits: Adding tax credits can reduce your tax liability.

8. Subtract your credits from your tax.

9. Healthcare: Individual Responsibility. See instructions for line 61 of Form 1040.

10. Other taxes: This section refers to self-employment tax, unreported Social Security and Medicare Tax, additional IRA tax, or advance EIC payments.

11. Total tax: This is all the tax you owe, minus your credits.


12. Federal income tax and other taxes already withheld: This includes anything you’ve already had withheld, plus any amounts you might have not included the first time around.

13. Estimated tax payments: Here you must input any estimated tax payments you already made for the year you’re revising.

14. Earned income credit: Enter the amount you took the first time, or an amended amount.

15. Refundable credits: There are many refundable credits that you can input here. If you didn’t complete one of these forms when you first filed taxes, now you can.

16. Total amount paid with request for extension of time to file, tax paid with original return, and additional tax paid after return was filed: This amount refers to any taxes you already paid with your original filing or prior 1040X.

17. Total payments: All of the above added up. These are the amounts that will offset your tax liability.

Refund or Amount You Owe

18. If you had a refund due to you on the original return, enter that amount here.

19. Subtract that refund, if any, from your total tax payments (line 17).

20. If the amount in line 19 is less than the amount in line 11 (in Column C), then you’ll have to pay an additional tax as a result of filing this amended return. If smaller, enter the amount here.

21. If the amount in line 19 is greater than the amount in line 11, you’ll receive a tax refund. If this is the case, enter the amount here.

22. If you are due a refund and want it sent to you, enter the amount here that you would like to be refunded.

23. If you’d rather apply this refund to your tax liability as an estimated tax payment, you can do that too. This means that the IRS will just hold on to the money for you, and you can use it as a credit on your next tax return.

1040X Part I: Exemptions

If you’re changing the number of exemptions, you’ll also have to fill out Part I of the 1040X to explain why you are changing it, and then break it down among the types of dependents in the provided chart. You need to list all of your dependents and their Social Security numbers and relationships to you, and whether they qualify for the child tax credit. If you aren’t making changes to your exemptions, you can completely ignore Part I.

Explanation of Changes

Here’s the fun part – this is where you get to explain why you need to amend the return. Keep it short, simple, and to the point. If you changed any forms other than your 1040, you need to include copies of the latest versions, and explain where you made changes and why.

Final Word

The IRS lets you get a do-over for up to three years after you file – so if you think you missed something, you have nothing to lose by checking. And if you find that you do need to make changes, it’s easy to fill out the form and send it in to receive what’s owed to you.

Have you ever filed an amended return? Did you receive a refund, or did you end up owing more money as a result?

  • harold doglus

    Hi, Kira:
    Thanks very much for your post that I urgently needed. I accidentally forgot to include my W-2 withholding on my 2011 tax return. As the result, I paid $1784 tax as I was supposed to have a $315 refund. I still have a few more questions about 1040x:
    1. Do I need to fill line 12-15 to arrive to line 16 total payment and subtract it from my total tax (line 10) if I don’t have other amend in the “Payments” section? I did have another payment deduction on my original tax return.
    2. To my understanding, I only need to fill out line 20-21 with a total amount of $2099 ($1784+315) because I didn’t have a tax refund. Am I correct? Thanks very much.


    • Kira Botkin

      If you don’t have anything to put in a line, 0 is an acceptable answer. But don’t send the IRS a form with only lines 20 and 21 filled out. You should fill in any lines for which you have an answer.

  • cartweet

    Hi kira:
    I need to file a 1040x because I forgot to fill out the dependent care section and missed a good chunk of refund. Is there anything else I need to include with the 1040x when I mail it out if this is my only change?

  • Frank

    My full time student son claimed himself as a deduction for tax year 2014 (earned $4090 during summer job). Can he file a 1040X, amend his return so I can claim him as a deduction/?