Which agency investigates potential violations of the Internal Revenue Code?

The Internal Revenue Service (IRS) is the agency specifically tasked with investigating potential violations of the Internal Revenue Code. This is because the IRS is charged with administering and enforcing federal tax laws, including the collection of taxes and the pursuit of tax compliance. The agency conducts audits, examines tax returns, and investigates fraudulent tax activities to ensure adherence to the tax code.

While the Department of Treasury oversees the IRS, it does not perform the investigative functions directly related to tax violations. The Federal Reserve primarily focuses on monetary policy and the regulation of banks, and U.S. Customs and Border Protection deals with customs and immigration enforcement rather than tax issues. Therefore, the IRS is the focal point for issues surrounding the Internal Revenue Code, making it the correct answer for this question.