How will you judge that the KPI and Deliverables are delivered on ground to the Client?

At first we should have a specific range of KPI in our mind, then we measure the KPI of our service or product if it's being delivered to the customers in the correct way, and if it's more than the KPI we expect or not.

We should firstly understand and determine the SLA that client need it and agreed with the client on that   , to make sure that the KPI Delivered to client ground you should have plane to your team PPM Plan and check physically the sites and you can initiate end users or client survey to make sure that all KPI are delivered probably   

Carrying out a survey is the best practice

First you need to know the needs of the client from this you can determine what specific KPIs you need, that enables you to monitor and evaluate according to a quantative record that would help you to make necessary decision or adjustments in taking corrective action that would definitely affect the entire business.