To enable warranty for inventory items, you need to enable the serial number-wise detail option in the inventory. To enable this, you need to follow the below steps:
Step 1: Go to Administration, then select Configuration, then select Features and Options.
Step 2: then select Inventory, enable the serial number-wise details option, and click on its configuration.
Step 3: and tick the maintain item serial number warranty also,
Step 4: After enabling this, you can maintain the item serial number warranty.
Step 5: Then, when you purchase or sell an item, you can define the warranty period for that item.