It bears repeating at this time of the year that the IRS will NOT call taxpayers regarding tax debts without first sending a specific letter about the debt in question. Even then the call would be questionable. They will NEVER ask for payment over the phone, and will NEVER imply or state that agents or police will make a visit to your home if you do not pay while on the phone.
If you receive such a call, hang up immediately, do not engage in conversation. Calls can be reported to Treasury inspectors at 1-800-366-4484 or by filing a complaint with the Federal Trade Commission at http://www.ftc.gov