Higher stockout costs due to lack of stock is one of the worst things that can happen to any online retailer. While in offline retail, a stock-out has the solitary impact of lost sales until the next batch arrives, in online retail, it means loss of ranking position, which has a much longer-lasting effect. What can a seller do to keep this from happening? Usually, retailers place all their focus on inventory replenishment. But the truth is that two lines of attack can help you avoid stock-outs—inventory and sales.