A change request comes into the picture whenever there is a request from the client for an addition or alteration to the agreed deliverables. A change request can also originate from internal reviews. This could be delivered as a planned release or a patch release for hot fixes or hardware upgrades. Primarily, a change request originates from the following sources:
Bugs identified during alpha or beta testing, or bugs/issues reported on the production environment by customers
A system/feature enhancement request from users
Changes in business rules
Requests from product management or the owner
For more details on change requests, you can refer to the following websites: