Purchases are offset by purchase discounts and Purchase Returns and Allowances. When it should be added depends on the Free On Board FOB policy of the trade. For the purchaser, this new inventory is added on shipment if the policy was FOB shipping point, and the seller remove this item from its inventory.
Purchase Definition of Purchase by Merriam-Webster.
The car was an expensive purchase. He displayed his recent purchases with pride. The ice made it impossible for the car's' wheels to gain a purchase on the road. The surface was so slick that the wheels couldn't' gain purchase.