Here's how to search a specific transaction: However, if you're trying to search the code using the Advanced Search feature in QuickBooks Online, this will only allow you to find a specific transaction type and not by item codes. You can search for an item using a code through the Products and Services section.
If you're trying to search the code from the Epos, you might need to add this product to your list so it will show when searching from the app. Thanks for getting back to us, meet-stylomobile.