we keep stumbling in our Pending invoices, because the check for duplicates is not checking the Pending Invoices also in review.

Workflow gets a message: Stopped (error): Posting of order canceled Invoice INV03876689 was already used on date 5/16/2022. ... We have to validate the Invoice was indeed updated / amount and information is the same ensure it is a Posted Invoice before clearing and deleting the Pending invoice.

Ideas Administrator

The feature is available: 
Vendor invoices overview - Finance | Dynamics 365 | Microsoft Learn

The user who submitted the invoice will receive an alert that an invoice was found that has a duplicate number. The user can correct the duplicate number before they resubmit the invoice to the workflow system. The alert will be shown if the Check the invoice number used parameter in Accounts payable is set to Reject duplicate. This feature is available if the Prohibit submission to workflow when the invoice number already exists on a posted invoice, and your system is not set up to accept duplicate invoice numbers parameter on the Feature management page is turned on.