What are the advantages of centralized contracting?

• Allows for fewer overheads.
• Duplication of staff efforts and resulting costs are negated and all activities are standardized.
• Many staff no longer have to spend time on low level ad hoc purchasing.
• Volume purchasing means that better prices, greater discounts and more agreeable terms can be obtained.
• Volume deliveries cut down on delivery charges and staffing costs to move and store the goods.
• Computerized systems can be used to automate much of the work as well as integrate the purchasing systems with accounting and stock control.
• Centralized records can be kept of all purchases.
• Staff can be trained in purchasing and how to minimize costs.
• Suppliers know where and whom to contact which makes supplier contact much easier.
• Purchasing staff can build good relationships with the buyers that enable the supplier to understand the business need and suggest other products that may be more suitable and cost effective.
• It allows for better control of inventories so that they can be kept at optimum levels.

As the question is not specific to any trade, I would say that centralized contracting is always the better choice as it provides more control on various trading items as well as reducing wastage by maximizing the use of the material on different locations and of course operation cost will be limited to one place only.