All futures products are delivered at a uniform price after trading, while treasury bonds futures correspond to as many as 34 kinds of bonds in the same period. Moreover, when the transaction finally needs to be delivered with different cash bonds, the amount paid by the buyer is not exactly the same because of the different bond varieties and delivery time selected by the seller. For every 100 yuan of treasury bonds, the amount actually paid by the buyer to the seller is the only "invoice price" of treasury bonds futures.

Under the system of "basket" of deliverable bonds, the contract seller has the right to choose the cheapest and most favorable bond to deliver to the buyer according to the difference of "invoice price", which is the "cheapest deliverable bond". The cheapest deliverable bonds can be found through the relationship between duration and yield. In short, the term is the term of the bond. For the national debt with a yield below 3%, the cheapest deliverable bond is the bond with the shortest duration; For the national debt with a yield of more than 3%, the cheapest deliverable bond is the bond with the longest duration. For the national debt with the same maturity, the highest yield is the cheapest deliverable bond.