The Internal Revenue Service (IRS) is the part of the Federal government of the United States responsible for collecting taxes and enforcing tax laws. The IRS decides how much tax is owed and collects the revenue on a regular basis. The IRS is the largest bureau in the United States Department of the Treasury. It is one of the world's most efficient tax collection agencies. The IRS processed over 224 million tax forms and collected over $2 trillion in revenue in 2004. 