Where the data for quantity reduction and inventory update in the sales report and cost report are read from?

Thanks for using QuickBooks Online (QBO) for managing the sales and inventory of your business, Richard.

I can see that one of the members of the Community has already responded regarding your question about the data for quantity reduction and inventory update. Here's the link for you to check: https://quickbooks.intuit.com/learn-support/en-us/reports-and-accounting/re-where-the-data-for-quantity-reduction-and-inventory-update-in/01/1530605#M233821

If you have any more questions or need further clarification on how QBO handles inventory and sales data, don't hesitate to post here in the Community.