I need to update a vendor's pricing via their spreadsheet of approximately 12,000 items. I only want to to change the cost and sales price. How????

I know that managing a large number of items and updating pricing can be a challenging task. The method for importing your updates depends on whether you're working with inventory items or non-inventory/service items.

QuickBooks Online's built-in Product and Services import/update tool requires you to include the Quantity on Hand when importing inventory items.

Even if you're only updating the cost and sales price, the system still prompts you to provide a quantity since it is essential for tracking inventory.

In this case, I recommend exploring third-party apps that integrate with QuickBooks Online. Look for an app that offers the flexibility to update inventory information, including costs and sales prices, without requiring manual input of quantities.

Before performing a mass update, it's always a good idea to back up your data or export your products and services. With a large number of items, such as your 12,000 products, using a third-party importer is the most efficient solution. 

If you only need to update the cost and sales price for non-inventory or service items, you can export your product and services list into an Excel spreadsheet. Please see the attached screenshot for visual reference.

When you re-import, leave the Quantity blank for non-inventory and service items.

We're still here to help if you have further concerns.