Continuation-in-Part Patent Applications: A Comprehensive Guide

photograph at Snowbasin Ski Resort
2002 Olympic Downhill Course at Snowbasin

Continuation-in-part patent applications are a strange type of continuing patent application.  They are a tool that can extend the life of a patent family and protect improvements to inventions covered by prior patents.  They have significant risks, however, and should be approached carefully.

Patents play a pivotal role in safeguarding intellectual property, fostering innovation, and providing inventors with exclusive rights to their creations.  Understanding the mechanics of patents and patent applications, and the way continuation-in-part applications affect them, is crucial for anyone involved in the innovation process.

Patent Applications Briefly

In the US, most patent applications are of two types: utility patents and design patents.  These applications are designed to protect inventions and ornamental designs.  However, a specific type of patent application has gained prominence for its flexibility and strategic advantages— the continuation-in-part patent application.  Most patent attorneys shorthand this as a “CIP” application.

Continuation-in-part patent applications have become a powerful tool for inventors and companies seeking to build their inventions into networked families of patents.  Unlike standard patent filings, a continuation-in-part application allows applicants to introduce new material and claims while retaining the priority date of an original application.

A CIP application can be instrumental in avoiding prior art, extending protection, prolonging the ability to file new patents, and out-maneuvering competitors.  There are significant limits, however.  These applications are not a patent panacea, and anyone considering filing one should talk with a trusted patent lawyer carefully over strategy.

Indeed, a continuation-in-part application addresses a fundamental challenge faced by innovators—how to adapt and expand intellectual property protection as ideas mature and new aspects of the invention come to light.  Here, I talk about what a continuation-in-part application is, what it includes, what are its pros and cons, and what could be considered when deciding whether to file one.

What are Continuation-in-Part Patent Applications?

Continuation-in-part applications are filed when a patent applicant needs to add subject matter to an existing patent disclosure.  New subject matter cannot be added into a pending patent application, however, so the applicant must file a new application that builds from the pending application.

The new application adopts and re-presents the existing subject matter and is called a continuation-in-part patent application.  It “continues” the old subject matter “in part,” and also presents new subject matter “in part.”

How a Continuation-in-Part Application is Different From Other Patent Applications

Patent applications can be original applications or continuing applications.  Continuing applications, by definition, continue an existing patent application with a priority or benefit claim.  This allows you to build “families” of patents by linking them together through priority claims.

An original patent application is the first application you file presenting a new idea.  Sometimes, that will also be the last patent application you file to cover the idea.  However, in many cases, there will be several ways to protect the ideas disclosed in the original patent application.  You can file continuing applications that stem off of the original application to cover the ideas differently.

The first non-provisional application you file is informally considered a “parent” application, and the applications that stem from the parent are “child” applications.  These applications have different names depending on what they present and why: there are continuation applications, continuation-in-part patent applications, divisional patent applications, and reissue applications.  Provisional applications usually are not considered part of a patent family because they expire after just a year.

For example, you might have developed a new machine for forming holes in a metal workpiece.  Your parent application might disclose all of the structure of the machine as well as the operation of the machine and what process it uses to bore holes in the workpiece.  Sometimes, during prosecution of the patent application, the patent examiner will issue a restriction requirement.

A restriction requirement is the Patent Office’s way of saying you have tried to claim too many inventions in one application and have created a burden on the examiner.  Usually, you have to split your application up in response to a restriction requirement.  In the above example, you might split it up by electing to continue forward with the product claims covering the machine’s structure and dividing out the claims that cover the process for operating the machine.

Those process claims aren’t lost, though.  Rather, you can now file a divisional patent application.  The divisional application would be directed to just the process claims.  So you would end up with two patents; an original parent patent covering the machine as a product, and a divisional child patent covering the machine’s operating process.  A divisional patent application is one kind of continuing application.

Continuing the example, you would file a continuation-in-part patent application if you had improved the machine.  Let’s say that the machine had always used a drill mounted for three-axis movement, and you had filed and protected that with patents covering both the structure and operation of the three-axis drill.  However, you later developed a rotating table on which the workpiece was held during drilling.  This improves the efficiency and speed with which the machine operates.  You could file a continuation-in-part patent application on this improvement because it would build from the original disclosure but also add new subject matter.

Moreover, you could file the continuation-in-part application with a benefit claim to either of the product or process patent applications, so long as they are still pending.  This allows you to build the patent family out in different ways and over different timelines, which can provide a significant competitive advantage, as discussed further below.

Contents of a Continuation-in-Part Patent Application

Continuation-in-part patent applications are similar to original patent applications in almost all respects.  They include a written description of the invention, drawings showing how the invention is made and operates, and claims reciting the protected aspects of the invention.

However, continuation-in-part applications also contain a cross-reference and a benefit claim.

A cross-reference is a section of the written description that simply calls out the parent application and the other family applications to which it claims a benefit.  The cross-reference will identify each patent application by number and filing date.  Some attorneys will also include the title or inventor names.

The benefit claim is made in the Application Data Sheet.  The Application Data Sheet contains information about the inventors, the applicant, and the patent subject matter.  It includes a section that identifies any benefit claims to prior applications.  In that section, you identify the prior application (or applications), their application number, filing date, current status, whether they have matured into a patent or not, and what the nature of the relationship is, i.e., a continuation, continuation-in-part, divisional, etc.

The information entered into the Application Data Sheet is important.  The Patent Office uses this information over anything presented in the cross-reference section of the specification to correctly identify the child relationship of the filed application.

Advantages of Continuation-in-Part Patent Applications

By far the biggest advantage of continuation-in-part patent applications is the ability to extend the life of a patent family with the introduction of new patentable subject matter.

Creating patent families can produce a huge competitive value.  When a patent family is managed so that it maintains at least one live patent application in the family at all time, it creates an extended opportunity to file a new application to claim subject matter presented anywhere in the family.  This means that you can potentially write and file claims on subject matter that was disclosed five or ten years before and perhaps incorporated into a competitor’s product.

As an example, let’s return to the parent application on the three-axis drilling machine.  The application discloses how the machine is structured, assembled, and operated.  However, for some reason, the parent patent only claimed the machine as a product and did not claim how it operates.  Five years go by, but you have continued to file continuing applications, so that there is still one live patent application that claims a benefit all the way back to the original parent patent.  If a competitor launches a product that is different from your three-axis drilling machine but operates in a similar fashion, then you have no recourse, because you have no patent with claims covering its operation.  The competitor gets away with infringement.  Except, you still have the ability to file a continuing application into that family, because the family is still pending with one live application.  You could now file a new child application, write claims that describe the operation of the machine so that the competitor’s machine directly infringes.

Continuation-in-part patent applications are one type of continuing application that allow you to keep a patent family alive and pending.

A continuation-in-part patent application also allows you to incrementally protect improvements on ideas and inventions.  Because you cannot present new subject matter in an existing patent application, you use a CIP application to introduce the new matter.  For claims that relate entirely back to the parent subject matter, the prior art date claims priority back to the disclosing parent’s filing date.  Only the claims which incorporate new subject matter receive a new effective filing date.  By filing on incremental improvements, you can minimize the time between effective filing dates, which can reduce the risk that there has been intervening prior art which might defeat patentability of your improvements.

Although continuation-in-part patent applications certainly can present a large improvement, they often disclose only a small or limited amount of new subject matter.  For that reason, much of the disclosure is re-used from the parent reason, and so the costs of preparing a CIP application are usually much cheaper than filing an original patent application.

Lastly, because continuation-in-part patent applications of typically assigned to the same patent examiner who reviewed the prior application, you can usually receive faster examination on the CIP application.  Rather than waiting one or two years (if a request to expedite or make special is not made), the Examiner might pick up the CIP application and review it after just three months or so.

Disadvantages of Continuation-in-Part Patent Applications

You must be careful to correctly identify every patent application with its proper type.  If you present new subject matter in a patent application and don’t title it a continuation-in-part application, you will receive a rejection which can sometimes be administratively difficult to overcome.  Alternatively, if you identify a patent application as a continuation-in-part application when it does not present new subject matter, there may be questions about whether or why there is new content.  That can potentially create issues both in prosecution and litigation.

The new subject matter contained in a continuation-in-part application will receive its own effective filing date.  But, the life of the patent will usually be cut short, especially if the Patent Office makes a double patenting rejection.  A double patenting rejection essentially prevents you from extending patent protection on an invention, or on an obvious variation of an invention, by filing two separate applications on that invention.  There are limitations to double patenting rejections, and ways to argue over them, but often the patent applicant will choose to file a terminal disclaimer which cuts the life of the CIP short.

That gets to another risk of a CIP application.  The entirety of a patent lives and dies as a whole.  It isn’t as if some claims in a patent can expire after other claims in that same patent.  Therefore, if you are filing a CIP and some of the claims relate back to a parent application, but other claims are entirely new, those other claims are going to expire earlier than had they been presented in their own application without any benefit claim.  So if your improvement is entirely new, and you aren’t worried about whether your own prior patents will be cited against your new application, it may be smarter in some circumstances to file an original application rather than a continuation-in-part application.

Another risk: arguments made in the parent application can potentially be used against a patent issuing from your CIP application.  This is known as prosecution history estoppel.  It is sort of the Miranda rule for patents: anything you say in the prosecution of a patent application can later be used against you during litigation of the patent issuing from that application.  Usually, estoppel applies to the patent arising from the application, but it can also be used against child applications in some circumstances.

Filing continuation-in-part applications also increases the complexity of a patent portfolio.  Because CIP applications present new subject matter with its own effective filing date, tracking dates such as foreign-filing deadlines can be more cumbersome, especially without the use of specialized docketing software.


Continuation-in-part patent applications are not as simple as adding material, identifying the application differently, and filing.  They involve careful strategic choices, with risks and benefits affecting that decision.  If you are building a patent family, or need helping managing a portfolio of patents, or are considering filing a continuation-in-part application, please contact Phoenix patent attorney Tom Galvani at 602-281-6481 for more information.  Tom does not charge for initial calls and consultations and is happy to speak with you.

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