You can apply Credit Approval to Clients and Jobs meaning that Jobs cannot be set to a "Won" status if credit approval has not been confirmed at the Client level.
This feature is enabled in Tools & Settings > Job Settings > Financial Settings
If enabled then a option called "Credit Approved" will appear in the Invoicing Details section of the Client record:
If this is set to "Yes" then Jobs can be freely set to a Won status in the Job record.
If this is set to "No" then the "Won" statuses will not appear within the Job Status drop down list, physically preventing Jobs from being set to a "Won" status if credit has not been approved:
