The National Tax Agency takes charge of the execution side of the taxation business of assessment and collection of an internal tax for realizing fulfillment of a tax payer's spontaneous tax (excluding customs duty, tonnage due and special tonnage due) liability appropriately and smoothly. In enforcing tax, the Agency manages various activities on the basis of integration of examination and guidance, improvement of tax consultation, and active pursuit of public relations activities.

The Head Office of the National Tax Agency develops overall policies and plans for the administration of internal taxes, and supervises the activities of the Regional Taxation Bureaus and the Tax Offices. The Regional Taxation Bureaus, while guiding and supervising the administrative work of the Tax Offices, conduct investigations, examinations of large companies, and collection on large cases of overdue and delinquent taxes. Tax Offices provide consultation to the taxpayers, and are the front-line administrative bodies for administrative work on the assessment and collection of taxes.

The Agency also has an affiliated institution, the National Tax College, which administers training programs for tax officials, and a special institution the National Tax Tribunal, which reviews requests by taxpayers for reconsideration of tax controversies.