@smartin2

What is the Source Data for these services?

If you know the Source data is Timesheets, for this: "I want to check at months end that invoices were dated correctly (we back date our invoice to match when services occur)."

Then you run Time reports, and you include in your Display the columns for Billed, Unbilled, and Not Billable. That's how you review if Billable time got Invoiced. Example:

In Nov, I invoice at the End of the month for all time in that month. That means the Timesheet reports with tasks from all of Nov, is what I examine.

Please see my attachment.

Or, your services are performed by subcontractors, so you run Unbilled Costs by Job, for the date range in Nov, and change the Unbilled Filter to Any. Now you see them as Billed, Unbilled and Not Billable.