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 spyglass 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.

• 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 field should be positive,
• When you apply a gift card to customer's invoice the qty field should be negative.