Complex sentence: The IRS is responsible for collecting taxes and administering the Internal Revenue Code, the federal statutory tax law of the U.S. Its duty to maximize tax revenue entails providing tax assistance to taxpayers, as well as pursuing and resolving instances of erroneous or fraudulent tax filings.
Split into simpler sentences: The IRS is responsible for collecting taxes and administering the Internal Revenue Code, the main body of federal statutory tax law of the United States. The duties of the IRS include providing tax assistance to taxpayers and pursuing and resolving instances of erroneous or fraudulent tax filings.