CIC Services, LLC v. IRS

The Supreme Court unanimously held that the Anti-Injunction Act does not bar pre-enforcement challenges to regulatory requirements that are not themselves taxes, but are enforced through tax penalties.  The Anti-Injunction Act narrowly, but powerfully, forbids lawsuits undertaken for the purpose of restraining the assessment or collection of any federal tax.  Instead, a taxpayer must pay the tax and then seek a refund.  For tax penalties, that would mean deliberately violating a regulatory requirement and then arguing, in a refund action, that the requirement was invalid.  Even though some courts had construed the Anti-Injunction Act to sweep that broadly, the Supreme Court did not.