Why does an expense that is marked as billable for a certain customer, and shows up as un-billed activity, not create a non zero account balance?

Hello there, @drewschu.

Thank you for posting here in the Community and providing some details. I can share some insights on how the unbilled activity transactions are generated.

Unbilled activities are check or expense transactions that are not created as invoice yet in QBO. When creating a billable expense, make sure to link it on the invoice.

Here's what you need to do remove it from the queue:

1. On the Action column, click Start invoice.
2. On the Invoice window, click Save.

Creating a billable expense will only affect the Vendor's side. It's a non-posting transaction to Customer's balance until it is applied to an invoice.

For more details, please check this article: Enter billable expenses.

That's it. I'm still here to help you further if you have additional questions. Just add a comment below. Wishing you all the best!