Which type of regulation pertains to the Treasury Department's procedures?

The correct answer is administrative regulation. This type of regulation pertains to the rules and procedures established by government agencies, such as the Treasury Department, to implement and enforce the laws enacted by Congress. Administrative regulations are necessary to provide specific guidelines on how tax laws should be applied and adhered to in various situations.

In the context of the Treasury Department, administrative regulations outline the procedural aspects that govern tax administration, including how taxpayers should report income, claim deductions, and report various tax-related transactions. These regulations are important as they help provide clarity and consistency in tax compliance and enforceability.

Proposed regulations, while significant, refer to initial drafts of regulations that the Treasury Department issues for public comment before they become finalized. Guideline regulations generally do not carry the same legal weight as administrative regulations and are often used to offer general advice rather than enforceable rules. Enforcement regulations focus specifically on the actions and measures taken to ensure compliance with tax laws but do not capture the broader procedural aspects that administrative regulations cover.