What is the maximum stock / inventory items that can be loaded on QB advanced ?

Hello, @serena9. 

In QuickBooks Online Advanced, there are no usage limits for list items, which includes your stock and inventory items. You can add as many as you want.

If you haven't yet manually added stock items in your QuickBooks, follow these steps:

1. Head to the All apps menu on the left side of your screen. 
2. From the Sales and Get Paid section, select Product & Services. 
3. Click New to add a product or service, then select Stock item.
   

If you choose to import your products and services into QuickBooks, you can only import 1,000 rows at a time. If your list exceeds this limit, split it into multiple, smaller files for successful import. 

To know the usage limits for each subscription level, feel free to read this article: Learn about usage limits. 

Your questions are always welcome here in the community space.