Tax deductions come in so many flavors that it can be easy to overlook one. If you forgot to claim, say, some tuition expenses or a tax-deductible portion of your auto registration, it'd be great to be able to go back in time, fix the mistake and get your money back. Well, the Internal Revenue Service lets you do just that with Form 1040X, the "Amended Individual U.S. Tax Return." And for real back-in-time flair, you even get to fill out the form on paper.
1040X Marks the Spot
To claim a previously unreported tax deduction, you'll need a copy of Form 1040X, which you can download from the IRS website. You must use the paper 1040X regardless of which form you used for your original return -- 1040, 1040A or 1040EZ -- and regardless of whether you filed electronically or on paper. If the deduction applies in more than one year, you must fill out and send in a separate 1040X for each year.
Back in Time
For most overlooked deductions, the deadline for filing an amended return is three years from the due date of the original return you're correcting, or two years from the date you paid any tax from that return, whichever is later. Say it's the year 2015, and you wanted to amend your return for the 2012 tax year. That return was due April 15, 2013, so you would have until April 15, 2016, to file a 1040X. Even if you were a model citizen (and an accountant's dream client) and had filed your return in January 2013, you'd still have until April 2016. If for some reason you hadn't actually paid the tax due from that return until July 2014, then you would have until July 2016 -- two years -- to amend your return. One more thing: If you had received an extension to file the original return, your three-year clock starts ticking when the IRS receives your return, regardless of the deadline provided by the extension.
In certain situations, the IRS allows for more time to file an amended return, but these aren't the kind of things most taxpayers ever have to deal with. For example, you have 10 years to claim a deduction for tax paid to a foreign government, and seven years if you discover that a stock you owned has become worthless -- literally worthless, as in no value whatsoever. The instructions for Form 1040X outline other exceptions, but if you're in this kind of boat, it may be best to check with a tax professional.
Getting It Done
When you download the 1040X, go ahead and download the instructions, too, and they'll tell you exactly where to report your previously unclaimed deduction. Basically, you'll be identifying which numbers on your original return are wrong, providing the correct number and then, on the back, explaining the reason for the change. If amending your return involves making changes to other forms -- such as Schedule A, your itemized deductions -- attach updated copies of those forms to your 1040X. When you're done, stick the whole works in an envelope, put a stamp (or two) on it and mail it to the address identified in the 1040X instructions. The IRS wants a hard copy, so you can't e-file. Sorry.