Let's make sure you'll be able to inactivate your vendors, linda-beeson-bee.

Ideally, you'll have to open the unbilled charges so you'll be able to delete the transaction. 

From there, you'll have an option to delete transactions under the Action column. You'll just have to click the drop-down arrow and select Delete. After that, you can now inactivate your vendors or customers.

However, if you're getting the error when deleting the customer or vendor, it's possible that there are still transactions attached to your unbilled charges for your customer or vendor. You can check your bills and expenses preference and manage your customer's charge, and billable expense charge. To give you a detailed steps on how you can do about it, check out this article for your guide: Delete Customer With Unbilled Charges.

Furthermore, to make sure that you're data is accurate and that you're getting the information you need, you can run reports and customize them to keep track of your transactions. Go through this article for your reference: Customize Reports In QuickBooks Online.

Reach out to us if you have any concerns with your unbilled charges. The Community always ensures that we always get you covered with everything you need.