Scheduling of delay-tolerant jobs has been proposed as a mechanism to alleviate pressure on congested network resources. However, when multiple competing users share these resources, they may not be willing to reveal how flexible is the schedule for their jobs. This work presents a trading system that enables the users to trade their finite allowances in an scenario where they have fixed-size atomic jobs. The trading system makes it possible that tasks with strict timing requirements are completed on time, and flexibility is rewarded with either a larger share of the off-peak capacity or a lower total cost for their owners. The trading system is proven to always converge. Simulation on real traces show significant reductions on the peak-to-valley ratio on the link utilization.