The twist? Authorities claimed Microsoft “unjustly enriched” itself by using a six-monthly tax filing option; even though the law allowed it. The court slapped that down hard: "No statute creates 'unjust enrichment' for timely payments." This sets a crucial precedent: if you comply with the rules, the government can’t invent new reasons to charge you interest. Tax planning within legal boundaries? Totally legal. Tax officers second-guessing smart compliance? Not allowed. Big win for businesses; and a sharp reminder that rules mean something.