This article focuses on the barriers faced by firms due to non-compliance with European law. Although there is an extensive literature on non-compliance in the European Union, there has not been any systematic assessment of the barriers faced by firms in trying to market their products across different national boundaries. We draw on a comprehensive database of over 2000 cases of business complaints about regulatory and administrative barriers encountered in the single market. Our empirical findings survey the range and type of barriers that affect different industrial sectors, the variation in compliance with European law among member states, and the different solutions used to address business complaints about the functioning of the single market. The data shows that firms continue to face considerable challenges in operating the single market, and that there are still trade and growth dividends to be harnessed from addressing the remaining barriers to trade.