Understanding the distinctions of different types of patent applications is crucial for strategically managing a patent portfolio and securing the broadest possible protection for your inventions.

For this purpose we look at an imaginary patent family. A family of patent applications is based on the same invention.

Foundational Application: The Parent Application

Think of the parent application as the original, initial patent application filed for an invention. It lays the groundwork by disclosing the invention and claiming its novelty and inventiveness. All subsequent related applications trace their lineage back to this original filing.

Leveraging the Parent's Foundation: Priority and Subsequent Applications

A priority application isn't a specific type of application in itself, but rather a concept tied to an earlier filing. As explained in The concept of priority, filing a patent application in one country that is a member of the Paris Convention or the World Trade Organization (WTO), enables the applicant, within 12 months of that first filing date, file Subsequent applications in other member countries claiming priority to that first filing date. When filing subsequent applications, it is possible to include additional subject matter that was not in the priority application. However, the priority is only valid for subject matter that was part of the priority application.

This means the later applications with validly claimed priority are treated as if they were filed on the same date as the initial "priority" application for the purposes of novelty and inventive step. The initial application, in this context, acts as the priority application for the subsequent ones.

Branching Out: Divisional Application

In general, the examination of a patent application costs the same official fees for all inventions. There shouldn’t be a way to cheat the system by including multiple inventions in a single patent application to get these multiple inventions examined for the price of a single examination fee. In cases where the applicant files a patent application, that describes multiple inventions, the examiner will object that the application lacks “unity of invention”. The applicant needs to select a single invention that is examined in that application.

However, the inventions that were not selected are not lost. The applicant has the option to file Divisional applications that cover the other inventions. The divisional application is considered to have the same filing date as the parent application, and it consists of the same content as originally submitted with the parent patent application. At first sight, the concept of divisional applications may sound similar to the concept of subsequent applications. However, there are some fundamental differences between priority and divisional applications:

1. Divisional applications are always in the same jurisdiction as the respective parent application. A patent application in country A does not enable a divisional patent application country B.
2. Divisional applications can be filed as long as the parent application is pending. Once the parent application is granted or rejected, there is no possibility to file any divisional applications.

A divisional application "divides out" one or more of those distinct inventions from the parent application. Essentially, filing a divisional application is like splitting the original application into multiple applications, each focusing on a separate inventive concept disclosed in the parent application.

Building Upon the Original: Continuation Application

Filing a continuation application (sometimes called a "continuation without new matter") is at the applicant’s discretion. It allows to pursue further examination of the same invention disclosed in the parent application. This is often done when:

• the applicant wants to broaden or narrow the scope of the claims that were examined in the parent application.
• the patent examiner has allowed some claims but rejected others, and the applicant wants to continue pursuing the rejected claims.
• the applicant wants to obtain patent protection for different aspects or embodiments of the same underlying invention that weren't fully covered by the claims in the parent application.
• the applicant wants to keep a patent application pending for strategic reasons, such as to cover potential design-arounds by competitors or to strengthen their patent portfolio.

Adding New Developments: Continuation-in-Part (CIP) Application

A continuation-in-part (CIP) application as it exists in the United States, is not a standard patent application type in most other jurisdictions. The CIP builds upon a prior parent application but also introduces new matter – new features, improvements, or embodiments of the invention that were not disclosed in the parent.

The CIP application has a dual filing date:

• For the subject matter disclosed in the parent application, it claims the earlier filing date of the parent.
• For the newly added subject matter, it has its own, later filing date.

This is useful when further developments to the initial invention are made, after filing the parent application, because the applicant can maintain the benefit of the earlier filing date for the original aspects.