Statement of James R. White, Dir., Strategic Issues, GAO. Identity theft is a serious and growing problem in the U.S. Taxpayers are harmed when identity thieves file fraudulent tax documents using stolen names and Social Security numbers. In 2010 alone, the Internal Revenue Service (IRS) identified over 245,000 identity theft incidents that affected the tax system. The hundreds of thousands of taxpayers with tax problems caused by identity theft represent a small percentage of the expected 140 million individual returns filed, but for those affected, the problems can be quite serious. GAO was asked to describe, among other things, (1) when IRS detects identity theft based refund and employment fraud, (2) the steps IRS has taken to resolve, detect, and prevent innocent taxpayers' identity theft related problems, and (3) constraints that hinder IRS's ability to address these issues.This testimony is based on GAO's previous work on identity theft, which was updated by examining data on identity theft cases and interviewing IRS officials. Figures and tables. This is a print on demand report.