Enable Inventory System: Turn this option on to keep an inventory for all of the products and product variations in your store.
Note: The Inventory System will automatically disallow products with a zero inventory to be purchased from your website by default. You will have to enable the Inventory Backorders option to allow products with a zero inventory to be purchased.

Inventory Soft Limit: When a product's inventory reaches the Inventory Soft Limit number, a notification e-mail will be sent to you.

Default Inventory Quantity: Set a default quantity to use when creating new products or adding new attributes.

Enable inventory backorders: Turn this option on to enable backorders on your website. Backorders will allow the inventory for a product to reach a negative level.

Do not decrease inventory levels until an order is marked as reviewed: Inventory for your products will not be decreased until an order has been processed successfully.

Automatically hide product from store when it goes out of stock: When an item goes out of stock, automatically hide it from website.

Display While Supplies Last! on website for products at or below inventory soft limit: Display While Supplies Last! in red font next to the add to cart button on your website when a product reaches inventory soft limit.

Display Out Of Stock on website for products at inventory zero: Display Out Of Stock in red font next to the add to cart button on your website when a product reaches a zero inventory.

Display In Stock on website for products at inventory greater than zero: Display In Stock in green font next to the add to cart button on your website for products that are in stock.

Enable quickbooks inventory sync: Enable this option if you would like to synchronize your inventory levels with Quickbooks. Enabling this option will allow you to go to Store->Inventory Levels and click on Quickbooks Sync at the top of the page to configure your Quickbooks Sync settings.

Allow customers to automatically be notified via email when an item comes back in stock: Enable this option to allow customers to automatically be sent an email notification when an item comes back in stock. From the front-end product page, customers can add themselves to the instock notification list for an attribute or non-attribute item that is out of stock. Enabling this option will allow you to go to SEO-Cart->Configure->Product Page Template and configure various custom settings under the "Automatic Instock Notification" section.