Following the negative impact of the global economic crisis, the Southern African Customs Union (SACU) is facing a significant decline in revenue collections. This decline will have a large impact on transfers over the medium term to the smaller economies of SACU, namely Botswana, Lesotho, Namibia, and Swaziland (BLNS). This paper provides estimates of the revenue shortfall for each of the BLNS countries and proposes a strategy for the necessary adjustment to preserve fiscal and debt sustainability.