Someone with a foreign accent not even pronouncing some words correctly, claiming they were from The U.S. Treasury and if I did not call back it was considered a Federal Offense and Legal Action would be taken.  I have received calls 2 days in a row.  I was suspicious because the caller was speaking really fast and not in a very clear voice and unusual telephone call back number.  

Report the Calls to the real IRS here:
•report the incident to the Treasury Inspector General for Tax Administration at 800-366-4484.
•You can also file a complaint with the Federal Trade Commission at FTC.gov. Add "IRS Telephone Scam" to the comments in your complaint.

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Do consider maybe getting a call blocking device or phone.. You can google them and many are around $60.00 or so.

Allegedly from "US TREASURY REGARDING AN ENFORCEMENT ACTION".

Had a voice message from 323-686-3273 -- claims the caller (a male voice) is from IRS and that I or my lawyer should call return the call. Said it is a serious matter, blah blah blah. I note that it is similar to the message left a few days ago with the number 202-506-8649 (female voice, though it sounds like a recorded message). Message is about the same. I did not return the calls and I don't plan to.

Wow....The guy is nuts...He was quite pushy.