For a tax system to be fair and efficient, taxpayers must, at a minimum, be able to determine what they owe by consulting published codes. In the U.S., however, a new tax—the book minimum tax, also known as the corporate alternative minimum tax—went into effect at the beginning of 2023. The legislation establishing the levy is vague, and the Internal Revenue Service hasn’t issued clear rules. The lack of clear tax rules allows the IRS to write new rules during audits. It may even be unconstitutional: The lack of clear rules deprives taxpayers of due process, and delegating the definition of the tax to executive-branch agencies is a dereliction of Congress’s duty to write tax laws.

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