Just because you receive a check from the IRS does not mean that the money is yours. The taxpayer rightly turned back the money to the IRS. Here is the information as reported in USA Today.
USA Today, Cleveland Waitress Receives Huge IRS Refund Check by Mistake:
A longtime Cleveland waitress got the surprise of
her life this week when an enormous income tax refund check arrived in the
mail.When Ginny Hopkins filed her tax return, she expected a refund of $754 —
money she really needs to fix her car, among other things. Instead of that
check, she found a check mistakenly issued for $434,712 in her mailbox. ...
Hopkins knew that cashing the check could get her
in a whole lot of trouble. "They'll put me in Alactraz, waiting on the
night shift at Alcatraz," she said. "They'll reopen the place."
...
Hopkins made arrangements Wednesday to return the
check to the IRS office at the federal building in downtown Cleveland. Since
Hopkins needs the money right away, her friends at the restaurant and WKYC-TV
in Cleveland advanced her the money. The IRS said sometimes mistakes like this
happen, but it happens less often as more people file their taxes
electronically. Hopkins should get her correct refund check in six weeks, the
IRS said.