In order to use gift cards, first you need to create a new "part" category only for gift cards.
- Go to "Inventory management" / "Product/Job code management"
- Click on the spy glass next to category
- Click on the "+" sign and create new category.
- When you create it check "Inventory follow up" box and "Block list price inferior to the cost" box
- Leave unchecked "Allow product purchases" because you won't need to purchase the items in this category.
As soon as your Gift Card category is created you can start creating products associated to it.
- Go to "Inventory management" / "Product/Job code management" and click on the "+" sing to create a new product
- When you sell a gift card to somebody the qty filed should be positive
- When you apply a gift card to customer's invoice the qty field should be negative.