This article explores the extent to which EU law does and should enable undertakings to control which Member State’s contribution rate applies to them. By relying on posted workers, for example, undertakings can “shop” for the cheapest social security law, lowering their labour costs; this is, however, to the detriment of workers, competitors, and social security systems. The article seeks to determine when conflict rules excessively facilitate law shopping. It then discusses how legislators and courts can complicate law shopping by framing it as abuse, redesigning rules, interpreting them teleologically, and improving their enforcement.