The stock status of a product will NOT be changed by receiving a purchase order if the initial value of the stock status is NULL. Stock Status must have a positive, zero, or negative value, or the new stock will not be applied to the product.
By default, all products have a starting stock status of NULL. If you do not change the stock status, then any action that should affect stock status will not function properly (customer purchases, returns, received purchase orders, etc.). To keep a product's stock history accurate and functional, the product must have a non-NULL starting stock.
If the stock for a product is NULL, there will be a + [blank] next to Stock Status.
To add stock, simply type the number of on-hand units in the field and save. Non-NULL stock statuses will have a positive, zero, or negative value next to the Stock Status field.