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


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There are plenty of common tax filing errors. When you discover an error on your return, alarm bells go off. Will the IRS audit your tax returns for the past decade? Will you be arrested for filing a false return?

Never fear; Form 1040X is designed for just such a circumstance. And lest you think you’re the only person who’s made a mistake on a federal tax return, relax. According to the IRS, you’re in good company. The IRS estimates that nearly 6 million amended returns were filed during the 2018 calendar year. Since they projected more than 156 million individual returns would be filed that year, that amounts to about 4% of all returns being amended. See, you’re not alone!

Here’s everything you need to know about filing a Form 1040X. For help with other tax filing issues, check out our complete tax filing guide or talk to a tax advisor from H&R Block.

Form 1040X Basics

Form 1040X is the Amended U.S. Individual Income Tax Return. It’s a two-page form used to amend a previously filed individual tax return. This form allows you to make corrections to your submitted return or change amounts on the return that the IRS may have adjusted after submission. The possible outcomes of amending are that you get an additional refund, have to repay part of the refund you already received, or have to pay additional tax.

Note that you cannot e-file Form 1040X. You must mail it with supporting forms, schedules, and source documents, such as a W-2. In order to prepare an amended return, you’ll need a copy of your original return, new source documents or other information that will change, such as filing status or dependents, and Form 1040X.

When to File

If you’re due to receive a refund on your originally filed return, the IRS recommends waiting until you receive that refund before submitting an amended return. That way, you know the IRS has finished processing your return, and there’s no change your amended return might be processed before the original return, causing the IRS a lot of confusion. It could even result in delays in processing your refund and you spending more time responding to IRS notices to get the situation sorted out.

Generally speaking, you have three years from the due date of your original tax return to file a 1040X to claim a refund. You can file the 1040X within two years from the date you paid the tax if that date is later than the filing date. Review the 1040X instructions for special rules that apply to certain situations.

How to File

Page one of Form 1040X has a header section with information similar to the regular 1040. The first step is to check the box indicating which tax year you’re amending. If you need to amend more than one year’s return, fill out a separate 1040X for each tax year.

Then, enter your name and Social Security number and the same data for your spouse, if you’re filing jointly. Enter your current address and daytime phone number, then enter your filing status, whether you’re changing it or not.

Next is the section where most changes usually occur. The left-most column has descriptions and instructions under the following general headings:

  • Income and Deductions
  • Tax Liability
  • Payments
  • Refund or Amount You Owe

The right three columns are for numbers:

  • Column A: Original Amount
  • Column B: Net Change
  • Column C: Correct Amount

Start by putting the amounts from your original return in Column A. Then, put the increase or decrease in Column B. Combine the amounts in Columns A and B and enter the result in Column C. If there is no amount in Column B because that line isn’t affected by the change, then you’ll re-enter the figure from Column A is in Column C. Show any negative items in parentheses; for example, -234 would be entered as “(234).”

An Example of How to Fill Out Form 1040X

Let’s walk through amending the 2018 return of John Taxpayer, a single person with no dependents. On his original return, John’s adjusted gross income (AGI) (Line 7 of Form 1040) was $23,000. After filing his return, John received a second Form W-2 with $1,500 of wages in Box 1.

Income & Deductions

In the Income and Deductions section of Form 1040X on Line 1, John would enter $23,000 in Column A and $1,500 in Column B. The amount in Column C would be $23,000 + $1,500 = $24,500.

On his original return, John opted to claim the standard deduction of $12,000 for single taxpayers rather than itemize his deductions. That won’t change on the amended return, so John enters $12,000 in Column A, nothing in Column B, and $12,000 in Column C. Then he subtracts the amounts on Line 2 from the amounts on Line 1 in each column and enters the results on Line 3 in each column. This action reduces his AGI by the amount of the standard deduction.

Line 4a doesn’t apply to John because the Tax Cuts and Jobs Act of 2017 eliminated the personal exemption for tax years 2018 to 2025. If he were filing an amended return for the tax year 2017 or prior, he would enter the personal exemption claimed on his originally filed return here.

Line 4b also doesn’t apply to John because he didn’t claim the qualified business income deduction on his 2018 return. This is a new deduction starting with 2018 returns, also a result of the Tax Cuts and Jobs Act. Since John doesn’t have a pass-through business, it doesn’t apply to his return.

Since he didn’t enter anything in Lines 4a or 4b, John simply carries the amounts from Line 3 to Line 5 in each column. On his originally filed return, his taxable income was $11,000 ($23,000 of wages minus the $12,000 standard deduction). His new taxable income for 2018 is $12,500 ($23,000 + $1,500 in wages minus the $12,000 standard deduction). This section is now complete.

Tax Liability

Having arrived at the original and amended taxable income amounts, John now enters his tax amount on Line 6 in the Tax Liability section. On his original return, John’s tax was $1,133, so he enters that amount into Column A.

To calculate his new tax liability for 2018, John goes to the 2018 Tax Table in the 1040 instructions and turns to page 69. In the section labeled “12,000,” he finds the tax bracket $12,500 to $12,550. In the column labeled “Single” (his filing status), he finds the tax amount of $1,313, which he enters on Line 6, Column C of the 1040X. The difference between the two numbers ($1,133 and $1,313) is $180, which goes in Column B.

John did not claim any credits on his 2018 return, so there’s nothing to enter on Line 7. He repeats the amounts from Line 6 on Line 8. Similarly, John does not have to pay the penalty for failing to carry minimum essential health coverage or owing any other taxes, so he’ll repeat the amounts from Line 8 on Line 11. His total tax on Line 11 is $1,133 in Column A, $180 in Column B, and $1,313 in Column C.

Tax Payments

Moving on to the “Payments” section, let’s suppose John’s original return had withholding of $2,100 (shown on Form 1040, Line 16), and the new W-2 shows withholding of $300 in Box 2. On Form 1040X, Line 12, in the “Payments” section, John would enter $2,100 in Column A and $300 in Column B. Column C would show $2,100 + $300 = $2,400.

John isn’t eligible for any tax credits and didn’t make any estimated payments, so Lines 13, 14, and 15 are blank, as is Line 16 since he didn’t file for an extension. So, on Line 17, we add Lines 12 through 15 in Column C and Line 16, for a total of $2,400.

Refund or Amount You Owe

In the “Refund or Amount You Owe” section of 1040X, John finally finds out if he has to repay part of the refund he already received.

On Line 18, he enters the refund amount he previously received – $967 in this case. This amount is the difference between Column A, Lines 12 and 11. He subtracts that amount from the new withholding amount (Column C, Line 12) and enters the result ($1,433) on Line 19.

Now, John compares that amount to the amount on Column C, Line 11. Since the liability ($1,313) is less than the figure on Line 19 ($1,433), he subtracts and put the “amount overpaid” ($120) on Line 21, then enters that amount again on Line 22.

The verdict: John is getting a refund. If he wanted, he could enter $120 on Line 23 instead of Line 22 and have his overpayment applied to another tax year.

Explanation of Changes

Now it’s time to move on to Page 2, Part III of Form 1040X, where John explains to the IRS exactly what it is that he’s amending on the return. He skips Part I because that section only applies if he’s changing the number of dependents claimed on his 2018 return or changing exemptions listed on returns filed for 2017 and earlier. He also skips Part II, which only applies if he wants to change his $3 contribution to the Presidential Election Campaign Fund.

Moving on to Part III, John will first make an overview statement explaining why he’s amending the return – for example, “Amending to add W-2 income not initially reported.” Then, he explains the details:

  • Lines 1, 3, 5: Adjusted gross income and taxable income increased by $1,500
  • Lines 6, 11: Tax and total tax increased by $180
  • Line 13: Withholding increased by $300
  • Line 21: Additional overpayment of $120
  • Line 22: Amount to be refunded: $120

Sign, Date, Assemble, and Mail to the IRS

John is almost done now. It’s time to get the amended return finalized and ready to send off to the IRS. First, he needs to sign and date the 1040X. He also needs to assemble the documentation he needs to submit with the 1040X.

He’ll include a new, corrected Form 1040 for the tax year he’s amending and mark it “As Amended” at the top of each page. If his amendment changed any other forms or schedules attached to Form 1040, he’d include those as well. He’ll also include a copy of any source documents that necessitated the amendment – in his case, a copy of the new W-2.

To find out where to mail this stack of paperwork, John will look in the 1040X instructions. On page 17, under “Where To File,” he’ll find his state on the left and the corresponding IRS address on the right.

Be sure to keep a copy of all of the paperwork for your records. As always, when mailing something to the IRS, it’s a good idea to send it via certified mail. If your amended return gets lost in the mail or arrives late, the IRS won’t accept first-class mail as proof you mailed your 1040X on time.

Note that starting with 2019 tax returns, the IRS now allows you to electronically file Form 1040X. If you filed your 2019 tax return using tax preparation software like TurboTax or H&R Block, follow the instructions in the software to amend and e-file your return. For any year before 2019, you still need to mail the paper forms.

Other Scenarios

In our example above, we only covered one scenario: amending to add additional income. You might also amend a return to change your filing status, add another dependent, or claim a credit you forgot.

For example, let’s say you just found out that your ex-spouse didn’t claim your son as a dependent for the 2017 tax year and signed Form 8332 releasing the right to claim the exemption to you. However, you didn’t find out about this until after you filed your 2017 return. You would go to Page 2, Part I, Exemptions.

On Line 24, list one exemption for you – and one for your spouse, if you’re married filing jointly – on the original return. On Line 25, add your dependent(s), then the net change of one (Column B) and the correct number of one (Column C). On Line 28, put the total number of exemptions on the original return, the net change, and the correct total in Columns A, B, and C, respectively. On Line 29, multiply the amount of an exemption for 2017 ($4,050) times the numbers on Line 28 for each of the three columns. Transfer these totals to Line 4a on Page 1 and then work through the rest of the calculations.

As we mentioned above when reviewing the Income and Deductions section, the Tax Cuts and Jobs Act eliminated the personal exemption starting with the 2018 tax year. If your ex released the right to claim your dependent for 2018 instead of 2017, you would still complete Part I to claim your son as a dependent, but you would follow the directions in this section for 2018 returns and leave Lines 24, 28 and 29 blank. Claiming your son in 2018 wouldn’t affect your exemptions for 2018, but it could open up the possibility of claiming the Child Tax Credit, the Earned Income Tax Credit, the Child and Dependent Care Credit, or an education tax credit.

If you qualified for a new credit, it would go on Page 1, Line 15, with the appropriate box checked. For example, if you added your son as a dependent and he qualified for the Additional Child Tax Credit, you would mark the box labeled “Schedule 8812” and put the amount on Line 15. Then you would need to attach the revised Schedule 8812 to your Form 1040X.

Keep in mind that you may also need to amend your state return. Each state has its own tax forms and rules for amending returns, so check with your state’s department of revenue for more information.

Final Word

Amending a previously filed tax return is nothing to be afraid or ashamed of. It happens a few million times every tax season. Documents get misplaced or arrive late, you forget about a deduction you wanted to claim, or you read about a tax credit for which you qualify after you file.

Filing an amended return isn’t simple, but if you approach it systematically, it doesn’t have to be overwhelming. Plus, if you used online tax preparation software from H&R Block or someone else to file your return initially, the software usually makes it pretty easy to file Form 1040X without forcing you to run the calculations and know exactly where each number goes.

Once your amended return is finally done and sent on its way, you can breathe a sigh of relief. You can then track the status of your amended return three weeks after you file it by using the IRS’s Where’s My Amended Return? tool.


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Janet Berry-Johnson is a Certified Public Accountant. Before leaving the accounting world to focus on freelance writing, she specialized in income tax consulting and compliance for individuals and small businesses. She lives in Omaha, Nebraska with her husband and son and their rescue dog, Dexter.