Internal Revenue Service

Treasury Department agency charged with administering and enforcing federal tax laws, except those relating to alcohol, tobacco, firearms, and explosives. The IRS issues rulings and regulations to supplement the provisions of the Internal Revenue Code; determines, assesses, and collects internal revenue taxes; determines pension plan qualifications and exempt organization status; and provides certain taxpayer services such as publishing educational literature and adjudicating complaints. It maintains seven major regional offices in addition to its headquarters in Washington, D.C.