Once a patent application has been submitted it is possible to have an extension to the application. That means it is possible to make modifications, changes, addition or deletions to the submitted patent applications. The different types of extensions applications are:

Division application – Suppose the patent examiner feels that the basic application has covered two or more inventions, the examiner may require the application to be restricted to one of the inventions. The other “nonelected” invention will have to be filed as a separate application. This is done by filing a divisional application. The divisional application will be valid from the date of filing of the basic application and it can be an addition to the original application.

Continual application – Suppose the examiner sends a final office action (OA), to get another round with the examiner on the same claims, or a new and different set of claims, a continuous application that continues the original application can be filed. The continuous application gets the benefit of the filing date of the original application.

Request of continuing examination - This application is allied with the continuous application and enables to get another round with the examiner on the same application. It is like a second chance on the path to a patent and it replaces the basic application.

Reissue application – The reissue application can be filed if changes have to be made to an original received patent. It is filed in case revisions of the claims have to be made or corrections of specifications have to be done. The reissued patent takes the place of the original patent.

CIP (continuation in part application) – If changes or improvements on the basic invention has to be made during the patent pending of the patent application or to obtain specific claims to the improvement of a CIP application will have to be filed. The CIP can exist with the original patent or can replace the basic application.

Substitute application – If an application is abandoned and is later re filed it’s called a substitute application. The substitute application has no continuity with the original application and no patent on the original application is possible.

Independent application – If major improvements have been made to the basic invention that uses new concepts and can really stand apart an independent application can be filed. An independent application is separate application from the basic application, although the basic application can be referred to.