If your case is in collections and you need to reach the Automed Collection System, commonly known as ACS within the IRS, you call several different numbers:
1) If you call 1-800-829-1040 between 7am and 7pm, they can help answer your questions and direct your calls to ACS if you need to speak with someone there.
2) If you know you are in ACS and are self-employed, then you should call 1-800-829-3903.
3) If you know you are in ACS and are a wage-earner, then you should call 1-800-829-7560.
Also, you can access more information about ACS and the IRS at www.irs.gov.