This number has been calling my husband's cell phone and claiming to be the IRS, supposedly suing him, etc.  The real IRS always mails the taxpayer several times if there is an issue. If they do not get a reply from the taxpayer, they will send a certified letter. If they still do not get a reply, then they may call, but they first ask to verify who you are, and they tell you that if you are uncomfortable giving out the last four numbers of your social security number, you can either go to a local office of the IRS and speak to them in person, or call the IRS using the phone number(s) listed at irs.gov.  The real IRS will NEVER demand a payment, claim they are suing, or threaten your arrest if you do not pay immediately over the phone.

The irs.gov website also has warnings on their site about scam calls like this.  Do not be suckered!  It is a TOTAL SCAM!!!