Only use Install Status. That is the only status Finance is going to care about. Finance doesn't only care if something is operational or non-operational. They care if it is on the books, what the CMDB Status is and what the depreciating cost of the device is that the CMDB record represents.

If you don't know it by now, Finance and Security are your biggest most valued partners, if you're using ServiceNow to perform Configuration Management. They can help you ensure everyone is following processes. And everyone listens to them. If you get them on your side you will have a much easier time getting everyone else on your side.