I am getting constant calls from this number, When I call it back they say get an access code. When I get the code from my business office I still cannot get anyone.

I got a recording from this number today.  Does not at all sound legitimate to me.

I just received a call from this number telling me I am being sued in court and must call ASAP to avoid legal proceedings. No names, just a recorded message.

I have this call saying he is an agent for the IRS and an audit on my back taxes states I owe thousands of dollars. My audit was for a 4 year period.

There is a widespread IRS or "tax scam" being  practiced by scammers on both Canadian and USA residents.
USA tax payers should read this:
http://www.irs.gov/uac/Newsroom/IRS-Reiterate ... -Telephone-Scam

Short answer:
The IRS never initiates a contact via phone.
They always send a snailmail first.

Educational post:
This scam is also described as scam #11, here:
http://phonehelp.2truth.com/facts_rev.html

If you were contacted by an IRS impostor, you may file a report, after clicking on this link:
http://www.treasury.gov/tigta/contact_report_scam.shtml