On 24 September 2019, the UK antitrust authority imposed a £250k fine on PayPal in connection with its acquisition of iZettle, a competing Swedish payment systems provider. This is the highest fine levied to date for a single violation of UK merger control rules. The fine came after the Competition and Markets Authority (“CMA”) held that PayPal had breached an initial enforcement order (“IEO”) by contacting UK-based customers about its acquisition during the CMA's merger review. The case illustrates that despite the UK being a voluntary filing jurisdiction, merging parties may need to be careful when engaging in post-close integration while an IEO is in effect. The case further sheds light on the limits of the otherwise rather liberal approach of the CMA with respect to the extra-territorial reach of their jurisdiction.