How do I revert an invoice to billable expense charges?

We can delete the invoice entirely so that the associated billable expense charges will reappear as open entries in the All Sales tab, @Jfekete. I’d be glad to share this in detail to help you get going.
 

When you delete the invoice, the associated billable expense charges will be restored as open entries. Once this is done, you can now convert them back into an invoice whenever you're ready.

Here’s a step-by-step process for you:

1. Navigate to Sales, then Customers.
2. Choose the customer for whom you’d like to revert the invoice back to billable expense charges.
3. Search for the invoice transaction and click the drop-down arrow in the ACTION column.
4. Hit Delete.
   

Once deleted, you can go to the All Sales tab to ensure the Billable Expense Charge transactions are now in an open status, confirming they are unlinked from the invoice.

Additionally, I recommend checking out this article to help you track bills and record payments in QuickBooks: Enter and manage bills and bill payments in QuickBooks Online. 
 

I’ve compiled the following resources to assist you in managing your customer’s charges, credits, and billable expense charges, as well as to help you delete other transactions in your books:
 

• Delete customers with unbilled charges
• Void or delete transactions in QuickBooks Online
   

Please know that we're here to provide continuous assistance and support if you need to delete, edit, or add other entries to your account. Don't hesitate to reach out if you need further help. We're committed to helping you every step of the way.