Suggestions for project work

Cannot get your query , can you plz elaborate with example.

Thanks sir. we are in signage business. we do work pan India. Our invoice values are usually more then 2 lacs. but we dispatch material part by part. after that we have to do joint audit with 3 rd party provided by client. once we done with audit we come to know our final billing amount. now tell me what is best possible solution for this. hope now it's clear