The Internal Revenue Service is the federal agency responsible for administering and enforcing U.S. tax laws. Its functions include collecting taxes, processing tax returns, issuing tax guidance, and supervising compliance with the Internal Revenue Code. Choice A is correct. The IRS does not regulate broker-dealers under the federal securities laws; that role primarily belongs to the SEC, while FINRA functions as a self-regulatory organization for broker-dealers. Choice C is not the best answer because criminal enforcement related to intentional circumvention of banking laws may involve law enforcement agencies and prosecutors, not the IRS as the primary securities-industry regulator. Choice D describes the Office of Foreign Assets Control, which administers and enforces economic and trade sanctions, not the IRS. The SIE outline identifies the Department of the Treasury and IRS under “Other Regulators and Agencies,” requiring candidates to understand the basic function of agencies that interact with the securities industry. The question is not asking about securities regulation specifically; it asks for the IRS’s primary governmental function. Reference: Knowledge of Capital Markets; Other Regulators and Agencies; Department of the Treasury/IRS.