The importance of global supply networks to the competitiveness of enterprises and national economies is growing. However, these benefits motivating firms to become global are coupled with the risks and uncertainties managers face in global supply networks. Customs clearance activities represent one of these risks. In e-commerce supply chains, the impact of customs clearance delays on corporate operations is increasingly pronounced. Organizations utilize a number of tactics and instruments to mitigate delays and ensure regulatory compliance effectively. For the development of successful strategies, the identification of uncertainties and their causes is vital. This study intends to evaluate the risk management techniques utilized to deal with customs uncertainty in cross-border e-commerce supply chains in Oman, as well as the influence of these techniques on customs clearance time and cost. A mixed-methods approach is used and employs a thematic analysis in the qualitative part followed by regression analysis to address the research issues in the quantitative part. Both qualitative and quantitative approaches have been employed in a complementary manner. Initially, semi-structured interviews were carried out with representatives from postal companies. A thematic analysis is used to investigate practically the uncertainties in customs practices and the risk management strategies employed to address these challenges. This was followed with a quantitative study conducted to explore the impact of certain proxies that act as risk strategies to reduce the time required for customs clearance. Secondary data was collected from the Directorate of General Customs to run the regression analysis using SPSS version 23.00. This study revealed from the interviews and subsequent regression analysis that organizations are selective in their use of risk management strategies depending on the expected clearance time and expected lane of shipment. This study provides valuable insights for parcel delivery companies in addressing the uncertainties occurring in customs and shed the light to those policy makers to know how they can improve the strategies better for ensuring a trade facilitation.