The Criminal Investigative Division of Internal Revenue Service (IRS-CI) does not just investigate tax fraud, but because of their renown skills for forensic accounting they are often used by prosecutors to investigate complex financial crimes.

FORBES: Broughton -- Rented Assets And Bogus Offshore Insurance Companies

Now the U.S. Internal Revenue Service (IRS) has an even bigger problem: the marketing of push-the-edge and over-the-edge shelters to the masses.

FORBES: U.S. tax rackets

You could use the online free file option provided by the Internal Revenue Service (IRS) (which has income limits), the online e-file option or various other free filing services available online.

FORBES: Simple Last-Minute Tax Tips

Enrolled agents are licensed by the Internal Revenue Service and must either pass a two-day test or have worked for the IRS for five years.

FORBES: Magazine Article