Options premium can prevent a product that is linked to an option selection from being added to the cart if the linked product doesn't have any stock in it. When this functionality is turned on and the product is out of stock, a message will display on the screen informing the user that the option product is out of stock and the user will be prevented from adding anything to the cart.
To enable this, follow these steps:
- From "Shopify Admin", select Apps.
- Select Product Options by Bold.
- Select Settings.
- Select Display Settings.
- Scroll down to "Inventory Checking", select the Enable inventory checking checkbox.
- Enter an Out of stock message.
- Enter a Not enough inventory for order message.
- Select Save.