The IRS annually lists the "dirty dozen" tax scams in an effort to protect the public and itself. This year, identity theft is ranked as the top of the dirty dozen scams.
Identity thieves use a taxpayer's identity to file a tax return and fraudulently obtain a tax refund. The IRS reported that it blocked $1.4 Billion from going to the wrong person last year. Small wonder identity theft is ranked no. 1.
Other scams include "phishing" (i.e. tricking people into revealing personal identifiers), hiding funds offshore, reporting false income and abuse of charitable organizations.
If you suspect you are the victim of tax return identity theft, you should contact the IRS immediately.