What would the workflow look like if subject milestones have not occurred but a payment has been received for these milestones?

What would the workflow look like if subject milestones have not occurred but a payment has been received for these milestones?

The payment will be held on account in Workday until these Milestones are completed and an invoice is received from OnCore. Study teams may create an invoice in OnCore for these outstanding Milestones but should only finalize the invoice with an invoice date once the Milestones have occurred.