http://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
http://800notes.com/forum/ta-8c2f64bf2b91fa5/irs-warns-of-telephone-scam

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.

This is a Pakistan or India based IRS scam. Do not fall for it. The IRS does not initiate any legal action via phone.  
Read http://www.treasury.gov/tigta/press/press_tigta-2014-03.htm

As general background information, here are a few things you can do:
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.

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)

3) If you are really annoyed: call or write to your representative in Congress. As these scams happen all over the country maybe this will trigger a reaction and provide US law enforcement agencies with the political backing and the resources they need to work in India and Pakistan together with local authorities (it can happen, read: http://www.ndtv.com/article/india/ex-call-cen ... mmission-320427). A US task force has already been set up in Jamaica to nab scammers there (see http://www.ice.gov/doclib/news/library/reports/cornerstone/cornerstone7-1.pdf). You can use the following template for your letter (more powerful!) or email:

http://800notes.com/forum/ta-a9526ebadc65cf9/ ... 558497927242748

Fake scammer from legal affairs department called on a VoIP line. Call trace geo-locates it in Pakistan. Some Islamic terrorists raising funds? Looting, plundering, scamming of non-Muslims has always been the Islamic way. The holy texts of Islam call it Ghanima and Fai. This is a scam using 202 and 415 area codes at least.

got call from this #:

"This message is intended to contact JL. Hi, this is James Howard with the Department of Legal Affairs and I was trying to reach you in regards to a very important issue. The number to reach me is 415-742-6882. If for any reason you are busy to call back, I would suggest you to have your retain attorney to do it for you, as delay in calling us might end up into a legal mess for you."

My parents got the call from John Howard asking for me too.  Too bad I haven't lived with them for several years.  They thought I was in some real legal trouble.   Glad I could show them it was a scam.  I've reported this number to the treasury and ftc as well.