In order to sell an item both in a package and individually as well, (for example a bottle of wine sold either by the bottle or by the case) you can use the Parent SKU settings. This is set from the Setup and Inventory menus.
The first step is to setup the parent SKU attribute by accessing the Setup menu.
From the setup screen, select the tab.
Now use the Attributes section to add the new parent SKU attribute.
1. Use the Attributes dropdown menu and set it to "SKU".
2. Name the new attribute "Parent SKU".
3. Set the format to "Text".
4. Once you have selected the previous options, press Add New Attribute and "Parent SKU" should be listed in the list of attributes.
Now that you have the attribute set, you can apply it to the items you wish by using the Inventory menu.
From the Inventory screen, select the tab in the top window and the tab on the bottom window.
Create a new SKU for the item that you wish to sell individually, and another new one for the boxed item (or select the items if you have already created them) and enter the details as normal. For example, create one SKU called "wine bottle" for the individual item, and another called "box of wine bottles" for the boxed item.
Now select the individual item. Using the Attributes section, go to the Parent SKU field and enter in the SKU of the boxed item.
Next, still keeping the individual item selected, use the PKG Qty field and type in the number of individual items in the boxed item. For example, there are 12 wine bottles in my box, so the wine bottle item has a PKG Qty of 12.
Press the button to save the changes. The parent SKU attribute will link the quantities of the two items together in the system, letting it know that 1 box of wine bottles equals 12 single bottles. If you sold 10 wine bottles in a sale, but your quantity on hand was only 3, the system would automatically remove 1 from the quantity of wine boxes, and add 12 to the quantity of wine bottles.