I am looking for a report that shows all expenses that have been allocated to a customer or project and whether or not it has been marked as "billable"

Hi, Melissa. The closest report that shows all expenses assigned to a customer or project is the Transaction List with Splits. I'll walk you through the steps.

Please note that QuickBooks Online doesn’t have a specific filter to display only expenses billed to a customer. However, you can export the report and manually remove transactions that don’t apply. Here’s how:

1. Navigate to the Reports menu.
2. Enter Transaction List with Splits in the search field.
3. Choose a Report period for the transactions you want to run.
4. Click the Customize option.
5. In the Filters fields, choose Transaction by type, equals, Bill, Billable Expense Charge, Cheque, or Expense.
6. In the Columns section, ensure that Transaction type and Customer are checked.
7. Click the Export icon so you can save and edit it outside QuickBooks.

Here's a sample of the report:

Please don't hesitate to reply if you need more assistance. We're just around.