This proof of concept (PoC) builds on an earlier feasibility study that identified blockchain technology as a promising enabler of paperless trade facilitation and enhanced trade competitiveness in Mongolia. That study highlighted five priority areas where blockchain-based solutions could enhance efficiency, transparency, and trust: customs clearance and border management; certificates of origin and trade documentation; traceability in mining and agriculture; trade finance and cross-border payments; and regional and multilateral trade corridors. Building upon the earlier study, this PoC focuses on the first identified area: Customs Clearance and Border Management. The PoC examines the use of sealing transit cargo documents and data to address legal requirements under the Mongolia Customs Law and to respond to identified operational challenges. The initiative is intended to provide practical insights into the technical and operational feasibility of blockchain-enabled solutions, without implying a commitment to full-scale implementation. Within the limited scope of the exercise, the PoC demonstrated that it is technically feasible to create a digital twin of a consignment at the point of entry, package the associated data and documents into a verifiable Document Pouch, and anchor cryptographic proofs using open standards. Overall, the PoC provides practical insights and a reference architecture that may inform future discussions on digital trade facilitation and customs modernization in Mongolia and the wider region with a blockchain-enabled approach. By adopting an incremental, evidence-based approach and leveraging open and interoperable technologies, policymakers and practitioners may be better positioned to assess how emerging technologies could be responsibly applied to enhance trust, transparency, and efficiency in cross-border trade.