What happened
When Uganda imposed a substantial levy on gold exports in the early 2020s, declared volumes fell sharply and refiners suspended shipments. The measure was subsequently restructured. The metal did not stop moving; it stopped being declared in Uganda.
The general rule
Fiscal instruments applied to mobile, high-value, easily concealed commodities need to be set below the cost of evasion, including the risk premium. Above that threshold the base disappears and receipts fall despite a higher rate.
Applying it now
The same logic governs the current value-addition levies. Charges that make domestic refining marginally attractive will be paid. Charges that exceed the cost of routing through a neighbour will not, and will damage the traceability the policy was meant to build.
Sources