How do I delete old products and services in my invoice section I recently took over my billing and the person before me has hundreds of useless products and services

I can see the importance of managing your products and services lists in QuickBooks Online (QBO), @clsprinkler. That's why I'm here to guide you how.

For the time being, you'll have to make your old products and service items inactive instead of deleting them completely in QBO. This is because we want to make sure your financial and inventory reports will remain accurate. 

1. Go to the Sales menu.
2. Select Products and services.
3. Mark the items you'd like to deactivate.
4. Click the Batch actions drop-down.
5. Select Make inactive.
6. Choose Yes to confirm.

I've attached a screenshot below for your reference.

Once done, the inactivated products and services will be removed from your lists of active ones on the Products and Services page. Then, I'd recommend pulling up the Product/Service Lists report. This is to view your complete list of active products and services, with their sales price, description, cost, and quantity on hand.

Also, I'm adding this article to further guide you in tracking your inventory in QBO. In case want to adjust an item's quantity without recording a purchase or sale to match what you have in stock, you can refer to this article for the complete details: Adjust inventory quantity on hand in QuickBooks Online.

Let me know if you have other concerns about managing your products and service items or your transactions in QBO. I'm just around to help. Take care always.