Discover what to do when HMRC issues a C18 Post Clearance Demand Note. Learn why these notices are issued, how to respond, and ways to manage and reduce additional duty charges. Ensure compliance and protect your business from unexpected costs. Harman Customs provides advice within the legal framework for customs rules & procedures for goods entering or leaving the UK & EU customs territories. We help importers and exporters build their customs compliance & minimise their customs taxes into the UK and EU.