Safety Stock

Safety stock is a term used to describe a level of stock that is maintained below the cycle stock to buffer against stock-outs.Safety stock is defined as extra units of inventory carried as protection against possible stockouts. It is held when an organization cannot accurately predit demand and/or lead time for the product.
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a level of stock over and above expected requirements held in inventory as a precaution against unusually heavy demand, delays in supply, etc.

the amount of inventory needed to protect against fluctuations in demand and lack of dependability of deliveries.