It is difficult to imagine but it is possible to file your tax return only to learn from the IRS that a tax return has already been processed under your name and Social Security number. It is a growing problem and a problem that has proven difficult to resolve.
Identity thieves who are able to get some basic information about a person will rush to file a fraudulent tax return before the victim does in the hopes that the IRS will send a refund to the thief. The victim then has a mess to sort out and needs to figure out what happened. This can be exceedingly difficult for the victim and even more difficult for those filing returns on the behalf of others, such as executors and guardians.
In the past, the IRS has not helped matters too much as the victim was not able to get a copy of the fraudulent tax return. However, as reported by the Wills, Trusts & Estates Prof Blog in "IRS Will Now Offer A Copy Of Fraudulently Filed Tax Returns To Identity Theft Victims," the IRS has changed its policy.
Now victims and their authorized representatives can get a copy of the return, which should help in figuring out what happened. The fraudulent return will be redacted pursuant to federal privacy laws, but not to an extent that would make viewing the return worthless.
It is wise to seek out a professional rather than handle it yourself if you have been a victim of a tax scam. And, you certainly shouldn't try to handle such a problem on your own if you are an executor or guardian.
Reference: Wills, Trusts & Estates Prof Blog (Nov. 30, 2015) "IRS Will Now Offer A Copy Of Fraudulently Filed Tax Returns To Identity Theft Victims"