Navigation: Sign into the Back Office for your Retail Store. On the left-side Navigation Panel, click Settings. On the Settings page, under Retail POS select Retail Settings.
The Retail Settings page enables you to configure Automatic SKU Code Generation and allow for negative inventory.
Automatic SKU CODE Generation - Allows for setting pre-defined SKU Code prefix. If enabled (set to YES), enter the SKU Code Sequence that will be established as the prefix when a SKU Code is auto-generated.

Allow Negative Inventory - If enabled (set to YES), negative inventory will be allowed while selling retail items.

When ready, click Save at the upper-right. The confirmation banner will appear.
