Beware of the CIP—Parent Applications Can Be Prior Art

Perkins Coie

Companies file patent applications with the United States Patent and Trademark Office (USPTO) to protect promising innovations.  Often, however, improvements, additional uses and refinements surface after filing a patent application.  How can a company capture these new, yet related, features?

The options available include filing a new application, a continuation application or a continuation-in-part (CIP) application. 

  • A new application is a straightforward option for protecting new developments, but it cannot take advantage of the priority date of the previously filed application (or “parent application”).  The priority date is important because the universe of references that the USPTO can use to reject a patent claim is fixed by an application’s priority date.  In general, the earlier the application’s priority date, the higher the chance of obtaining a patent.
  • A continuation application inherits the parent application’s priority date—but it is limited to the parent application’s disclosure.  New developments since the original patent filing cannot be described in a continuation application because new matter cannot be added to a continuation application’s disclosure. 
  • A CIP application permits a patent applicant to add new subject matter to the existing disclosure of the parent application while retaining the priority date for claims based on the original disclosure.  The claims of the CIP can be directed to the new subject matter, the old subject matter or a combination of the two. 

CIP applications used to be quite common, especially before mid-1995; in that era, the patent term was measured from the date a patent was issued.  CIP applications have now fallen out of favor.  The CIP application remains an attractive filing choice, but complications that may not be immediately apparent can offset its potential advantages.

Advantages of CIP Applications

The flexibility of a CIP application makes it an attractive option for several reasons.  First, a CIP application is designed to let the applicant add subject matter, unlike an ordinary continuation application.  The applicant can, for example, modify the existing disclosure, expand descriptions (e.g., to make sure that claims for an important feature are fully supported) or add paragraphs disclosing new subject matter. 

Second, an applicant can use a CIP application to economize on filing fees by combining old and new disclosures in one application, potentially reducing costs.  A CIP application can serve as a vehicle for future continuation applications as well.  Thus, an applicant can keep a patent family alive, making incremental improvements and adding embodiments that might not be sufficient to justify their own patent application, without needing to file parallel applications.

Third, claims that are limited to subject matter that the CIP application shares with the parent application inherit the priority date of the parent application.  By contrast, claims that include subject matter that is first disclosed in the CIP application are entitled only to the filing date of the CIP application.  In fact, a CIP application can have several priority dates; claims may extend back through “a continuous chain of copending nonprovisional applications” that disclose the claimed subject matter.  MPEP § 211.05(I)(B).  As a result, claims in a CIP application can have a priority date that is more than one year (e.g., three years) before the filing of the CIP application. 

A CIP application can be a convenient tool for the applicant to graft additional features onto a previously filed patent application.  It may not, however, be the right tool for the job. 

Pitfalls of CIP Applications

Shortened Patent Term

The standard patent term is 20 years after the application’s earliest priority date.  The patent term of a CIP application, which claims priority to a parent application, is thus limited to its parent application’s term.  For example, a CIP application filed in 2015 that claims priority to a parent application filed in 2010 will expire in 2030, as opposed to 2035 if the new disclosure had been filed in a standalone patent application.  The shortened patent term applies to all claims of the CIP application, even those that are not entitled to the parent’s earlier priority date.  An experienced patent attorney can help an applicant weigh the trade-off between an earlier priority date for some claims and a shortened patent term for all claims in a CIP application.

Claiming Any New Matter Brings Post-AIA Treatment

The earlier application (or chain of applications) to which a CIP application claims priority may well have been filed before implementation of the America Invents Act (AIA) changed the U.S. patent system in mid-March of 2013.  For new applications filed since then, the AIA replaces the old first-to-invent system with a first-inventor-to-file system and expands what can qualify as prior art, among many other changes.  A continuation application, however, not only inherits the parent application’s priority date but retains pre-AIA status if the parent application was pre-AIA.  A CIP application, on the other hand, can easily lose that status.  If even one claim in the CIP application includes subject matter introduced in the CIP after the AIA implementation date, the entire application will become subject to post-AIA treatment, along with any future applications that claim priority to the CIP. 

Claiming Any New Matter Spoils Priority

It is tempting, but incorrect, to think that a CIP application inherits the priority date of a parent application.  In a CIP application, individual claims have their own priority dates—and only a claim with all of its limitations fully supported by the disclosure of the parent application is entitled to the parent’s earlier priority date.  All other claims are given the CIP application’s later priority date.  

Consider, for example, a scenario in which a patent family includes a parent application “P” and a later CIP application “C” claiming priority to P:

  • Application P is published or patented, disclosing a process having steps 1–10.
  • Thirteen months later, application C is filed, disclosing additional step 11 and claiming both the 10-step process and a process having steps 1–11.

C’s claim of the 10-step process is entitled to P’s priority date, but C’s claim of the 11-step process is not.  As a result, references that came after P’s priority date can be cited against C.  Moreover, because P was published more than a year before C’s filing date, P itself can be cited as prior art against C’s claim for the 11-step process, including steps 1–10. 

An applicant’s own disclosure can sometimes be used to find a claim in a CIP application obvious.  If the CIP’s claim extends even slightly past what a parent application disclosed more than a year earlier, the parent can be used as prior art against the CIP claim.  See, e.g., In re Chu, 66 F.3d 292, 296–97 (Fed. Cir. 1995) (holding that even though Chu’s “application claims to be a CIP of the Doyle patent,” some claims were not supported by Doyle alone, so for those claims “the Doyle patent was properly relied on as prior art”); In re Van Langenhoven, 458 F.2d 132, 136–37 (C.C.P.A. 1972) (allowing “appellant’s own French patent” to be cited “to establish obviousness” of CIP claims for subject matter beyond the original disclosure, and remarking that “[i]t is of no avail to appellant that the Societe patent is his own”).

In a relatively recent case, Santarus, Inc. v. Par Pharmaceutical, Inc., 694 F.3d 1344 (Fed. Cir. 2012), the Federal Circuit addressed a situation in which a parent application was applied as prior art to render later CIP claims obvious.  At trial, the district court invalidated several Santarus CIP claims for minimum serum concentrations disclosed in the CIP and not in the parent patent.  The court found that the claims were not entitled to the parent’s priority date and held that they were obvious in light of the parent patent.  Santarus did not appeal the issue regarding the claims’ priority date, and the Federal Circuit panel majority affirmed the district court’s decision invalidating the claims.  See id. at 1352. 

In dissent, Judge Newman argued that a parent patent cannot be used as a prior art reference to a CIP patent claim.  Judge Newman focused on the content common to both applications instead of the new matter included in the claim; her reasoning would protect CIP claims from ever having their parent applications cited against them.  The majority of the Federal Circuit, however, has not followed that approach.  Priority does not belong to individual limitations within a claim.  The settled approach is that a CIP claim that is not supported by its parent application is not entitled to the priority date of the parent application, even for subject matter originally disclosed in the parent application.  See Studiengesellschaft Kohle, M.B.H. v. Shell Oil Co., 112 F.3d 1561, 1564 (Fed. Cir. 1997) (holding that an applicant must “meet the disclosure requirement of [35 U.S.C.] § 112, ¶ 1 in a single parent application in order to obtain an earlier filing date for individual claims”).

Practice Tips

A patent applicant can reduce risks associated with CIP applications by filing a CIP within a short time after the original disclosure (whether the disclosure was in the parent application or by public use, for example) and within a year of the original disclosure.  Ideally, if an invention has not been disclosed publicly outside the filed parent application, a CIP can be filed before the parent application is published.  Although intervening prior art can still be cited against CIP application claims, the original disclosure will not be available as prior art. 

In most cases, however, filing a continuation application based on the original disclosure or a new application with invention disclosures that are not obvious over the original disclosure will be a better strategy than filing a CIP application.  For example, if an applicant is interested in filing applications outside the United States, a CIP application may create issues that should be discussed with a patent professional.  


A continuation-in-part application may appear to be an attractive option but can lead an unwary applicant into such predicaments as a shortened patent term, lost priority and even obviousness over the applicant’s own patent applications. 

DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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