I received a phone call from this number 9/26/14 saying it was the IRS and I needed to call back.  I called back and a foreign-sounding male voice told me my tax return was incorrect and I owed the IRS money.  I told him to send me a notice in the mail regarding this and I will look into this with H&R Block who does our taxes.  I told him to stop calling my home.

See:  http://www.irs.gov/uac/Newsroom/IRS-Reiterate ... -Telephone-Scam

I received a call from 451-506-2388 on 09/26/2014 around 3:00 pm and again on 09/27/2014 at 5:42 am. I did not answer the call but when I heard the message stating it was the IRS I return the call. The person on the other end was speaking in a heavy accent sounding like he was from India or there about. I did not return the second call.

My mother received three phone calls on 9/26/14 from this number claiming to be the IRS.  The IRS NEVER initiates contact with taxpayers using the phone. See this IRS publication.  http://www.irs.gov/uac/Newsroom/IRS-Repeats-Warning-about-Phone-Scams

I received a call from 415-506-2388 which was just like the ones I received last week from 202-241-7388.  These are supposedly from agents of the IRS.  I used the links from RexIRS found under the 202-241-7388 search to report the calls to
1) Report it to TIGTA under http://www.treasury.gov/tigta/contact_report_scam.shtml especially if you have become a victim (lost money, gave personal information etc.). You can also file a complaint with the Federal Trade Commission at ftc.gov/complaint (include “IRS Telephone Scam" in your complaint). This way you can also help the government establish specific fraud patterns
and
2) Help kill their phone lines. The scammers use Voice over IP lines (e.g. magicJack (Ymax corporation)) to make it seem as if they are calling from the US. This is always against these companys' terms of service and can lead to immediate termination of their contract and blocking of their IP addresses for future attempts to register. Do a reverse look up of their telephone number (e.g. www.whitepages.com) to identify the Voice over IP provider and report it to the company and/or law enforcement (local police and/or state attorney general)