It would be more efficient for those submitting invoices (without the ability to confirm) to "Submit" an invoice (which would combine the check of policy, submission to approver and close the draft). Then, the permissions restrictions would change the UI depending on permissions to submit and / or approve.
For those submitting only - This change would eliminate the need to click on two buttons.
In short:
Employee with only permissions to draft an invoice would only see the "Submit" button which would check policy, submit and close the draft. These folks would not see the "confirm" button.
Employees that have permissions to submit and approve would see the "submit" and "confirm" button.