They said they were the IRS

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

Left a message stating she was with the IRS. It is a scam.  Another site said the number is owned by a service on Florida. I recently read these IRS scammers have collected millions.  What I don't understand is how they they aren't traced.

Exactly as above: Called by Julie Smith impersonating an IRS agent using this phone number: 202-241-7463

Apparently a major scam from overseas via VOIP lines

BEWARE!
This is one of several numbers for YMax Communications Corporation

I Googled YMax Communications, and they are the #1 worst source of complaints in the ComplaintsBoard.Com page.

According to many of the complaints posted, they do a LOT of lying (like saying you gave them your name & number at some prior event, or saying that you've been named in a lawsuit, or claiming that they represent the IRS, or offering ‘Free Government Grant money’ to recently-arrived foreigners, etc).  

One complainer said the people they spoke with at YMax had heavy Indian (or Pakistani?) accents, so they might be based beyond the reach of American laws and have the phone calls transferred to them from several US bases).

Based solely on my web research (and not on any personal experience), this is probably the worst telephone scamming operation I've ever heard about...