Reasons to use Purchase As
If you sell a product on multiple listings or under different SKUs but order it from your manufacturer as one SKU, you would set up a Purchase As to combine the sales and inventory data to obtain the total quantity to order from your manufacturer. For example, an Amazon seller might sell the same item through FBA as well as FBM. This seller will want to set a Purchase As to know how many units in total are needed to fulfill both product listings.
How to use Purchase As
Purchase As is a column that can be found in Manage Company> Items. This field is for you to input the SKU you purchase the item under if you purchase it as a different SKU than you sell it as. You can download data and upload with changes made if using this feature in bulk, or select the item under the "purchase as" column to input what item you will purchase it as.
When using the Purchase As, you are combining the sales and inventory information of the items together. When you go into Purchasing > Custom you will only see the "Purchase As" item since it is the only item available for purchase from your supplier. This also means you will only have one Item Card shown with the forecast, merged sales history, and inventory data for the "Purchase As" item. If you open the "Consolidate" portion of the Item Card, you will see all of the items included in the Purchase As. The "Consolidated Qty" column will show the forecast recommendation for each SKU based on the combined sales and the individual's inventory levels. The Purchasing gird columns Purchase Qty and Forecast Recommended Qty will provide the recommended units to order based on the data from all SKUs included in the Purchase As.