How do you handle change request?

The impact analysis document preparation followed by re-estimation is the process of handling change request. For example, a table of customer is available in the on going project. The customer also wants the addresses to assign to the project. For that a change request is raised and then an impact analysis of the same is performed. The estimation and the financial aspect of the project are known to the client. The implementation of this change request is continued by either by signing off the client or by agreement of the upper management.