This is not a legitimate call from the IRS.
Please visit our "Report Phishing" website (http://www.irs.gov/uac/Report-Phishing) and click on "Complaint Assistant". This will allow you to file a complaint with the FTC and identify the complaint as an IRS complaint.
Alternatively you can file a complaint directly with the FTC by visiting http://www.ftccomplaintassistant.gov.
Whether you use the IRS link or file the complaint directly with the FTC, add "IRS Hostile Call" in the Comments section of the complaint.
Since this individual is impersonating the IRS you should also report it to the Treasury Inspector General for Tax Administration (TIGTA). You can send an email to
[email protected] or file an online complaint by completing their "Online Form" located on their website, http://www.treasury.gov/tigta/contact_report.shtml.