What are the reasons that can influence the purchasing manager to buy and hold stock in the warehouse?

Best way to convenience the purchase manager give him adequate information and quality of products and competitive price and providing price compensation for quick sales. secondly you can inform him terms of payment which can be on sell out on monthly basis and procedure for returns of products. 

Inventory is an idle stock of physical goods that contain economic value, and are held in various forms by an organisation in its custody awaiting packing, processing, transformation, use or sale in a future point of time.

Any organisation which is into production, trading, sale and service of a product will necessarily hold stock of various physical resources to aid in future consumption and sale. While inventory is a necessary evil of any such business, it may be noted that the organisations hold inventories for various reasons, which include speculative purposes, functional purposes, physical necessities etc.

• All organisations engaged in production or sale of products hold inventory in one form or other.
• Inventory can be in complete state or incomplete state.
• Inventory is held to facilitate future consumption, sale or further processing/value addition.
• All inventoried resources have economic value and can be considered as assets of the organisation.

- Long shelf life of product

- Incentives and discounts received for large quantity purchase 

- Expectation of inflation of those items in future 

- High volume of consumption of that product