At the start, I review the workload and estimate the purchase value based on standard market pricing or the supplier’s initial quotations. Then we agree a minimum agent fee. If I manage to negotiate a discount or reduce certain costs later, the agent fee stays as agreed. If the scope grows during execution (more items, higher volume, additional suppliers — which means more workload), the agent fee is adjusted based on the final purchase value. This keeps incentives aligned — I can negotiate in your interests without working against my own.