By: Mark Magas  [8/24/22]

What is a Continuation?

After filing an original patent application, a patentee may file a continuation that claims priority to the original application. Think of a daisy-chain. Before prosecution of an original patent application ends, another starts.

A continuation is a separate patent claiming priority to the original patent that may include additional claims based on the original patent’s specification. There is no limit to the number of continuations a patentee may file.[1] The practice of filing continuations and always keeping one on file is referred to in the art as “keeping an open continuation.”

The claims in a continuation are limited to covering subject matter disclosed in the original patent’s specification.[2] If a continuation includes new subject matter beyond that described in the original patent specification, this is referred to as a “continuation-in-part.” With a continuation-in-part, claims based on the new subject matter are not given the benefit of the priority date of the original application.[3]

Divisionals are another close variant to a continuation and give rise to similar considerations. A divisional is usually filed in response to receiving a restriction requirement. This is where an examiner finds distinct inventions claimed in a patent application. A divisional allows a patentee to restart prosecution of the restricted claims as a separate divisional application that claims priority back to the original application.[4]

Benefits of Filing a Continuation

A continuation allows a patentee to obtain additional claims covering the original invention. This may be beneficial for several reasons, as explained below.

When considering the following benefits, reference this hypothetical patent claim for a chair:

1. A device made of wood comprising:

a base;

four legs; and

a back.

Obtain broader coverage

A patentee may write new claims that remove limitations or use broader language to cover additional embodiments. This is the most common use of a continuation. With the hypothetical chair claim, we could remove the limitation for “a back” to also cover a stool embodiment.

1. A device made of wood comprising:

a base; and

four legs; and 

a back.

Navigate around prior art

Often in litigation, a defendant will raise various prior art references to invalidate a patent. A patentee may write new claims that add limitations or use narrower language to circumvent the prior art. With the hypothetical chair claim, we could add a limitation for “two arm rests” to overcome a prior art reference that taught the basic chair.

1. A device made of wood comprising:

a base;

four legs;

two arm rests; and

a back.

Of course, it is also possible to both narrow a claim in some ways while simultaneously broadening the claim in other ways.

Adapt to evolving technology, law, market conditions, or litigation events

Technology is famously difficult to predict.

“Everything that can be invented has been invented.”

 –Charles H. Duell, Commissioner of the U.S. Patent Office (1889)

“There is no reason anyone would want a computer in their home.”

 –Ken Olsen, President and Chairman of Digital Equipment Corporation (1977)

Likewise, Congress may pass a new law or the courts may issue a new ruling that substantially affects the viability of a patent claim (e.g., the 2011 America Invents Act, which created the Inter Partes Review (IPR) procedure; or the Supreme Court’s decision in Alice Corp. Pty. Ltd. v. CLS Bank Int’l, 573 U.S. 208 (2014), which upended the law on patent subject matter eligibility). Market conditions may cause unexpected changes, such as if the price of a raw material or component substantially increases. Competitors may also try to design around a patent. And if a patent is in litigation, an unfavorable claim construction ruling may render a claim worthless.

Thus, a claim limitation that seemed appropriate when a patent was originally filed may not age well over the years. With the hypothetical chair claim, a number of events could happen that might affect the viability of the original claim: chair manufacturers may switch to using synthetic wood, which may not be covered by the original claim; a market shortage of wood may cause the commodity price to skyrocket, thereby causing chair manufacturers to switch to other cheaper materials not covered by the original claim; a competitor may decide to produce a chair with only three legs to design around the original claim. A continuation provides patentees some ability to adapt by writing new claims. So long as the new claims reflect what was actually invented at the start, the new claims get the benefit of the early filing date, which can be good for avoiding prior art.

Defer Important Decisions and Costs

Certain events may arise during patent prosecution that requires making important decisions impacting claim scope. This may entail a lengthy and costly fight with the Patent Office. For example, an examiner may find some dependent claims allowable, but not a broader independent claim. In a situation like this, it may be cheaper and more effective to limit the application to the allowed claims, obtain the initial patent right away, and then file the canceled independent claim as part of a continuation. This would delay important decisions and costs for some time.

Increase Market Value

Because of the benefits listed above, adding a continuation to a patent portfolio can increase the overall market value of the portfolio. One brokerage company estimated that keeping an open continuation increases the overall value of a patent portfolio with an issued U.S. patent by 10-25%.[5]

Discourage Catastrophic PTAB Litigation

When sued for patent infringement, a common and often successful strategy is to challenge the validity of the patents at issue through Inter Partes Review (IPR) proceedings at the Patent Trial and Appeal Board (PTAB).[6] An IPR is essentially a mini-trial, complete with briefings, hearings, and experts. This can be expensive for the challenging party, with costs typically ranging between $100,000 to $700,000, depending on the complexity of the technology.[7] Significantly, a party may only challenge a single patent in each IPR. Filing continuations thus makes this IPR strategy progressively more burdensome for potential challengers because there are simply more patents to challenge.

Drawbacks of Filing a Continuation

There are a few potential drawbacks to consider with filing a continuation.


Added cost is one obvious drawback. However, the cost to obtain a continuation is likely to be substantially lower than the cost to obtain the original patent. This is primarily because much of the work is already completed—a continuation uses the same patent specification as the original and any objections from the patent office are likely to involve the same or similar prior art that was raised during prosecution of the original application. The majority of work in a continuation is with drafting new claims, although these are often modeled after the existing claims.

Less Remaining Patent Term

Because a continuation claims priority back to the original patent, the continuation generally has the same patent term as the original patent. A patent term in the U.S. typically extends 20 years from the date of filing.[8] Thus, the expiration date of both the original patent and the continuation will likely be 20 years from the filing date of the original patent, although patent term adjustment may apply. When considering that prosecution of the original patent may take several years on its own, and the continuation a couple of years on top, the continuation patent may have a substantially shorter effective term.

Extends the Duty of Disclosure, Candor, and Good Faith

Another drawback to filing a continuation is that it keeps alive the patentee’s Duty of Disclosure, Candor, and Good Faith to the Patent Office. As part of this duty, a patentee must disclose relevant prior art to the Patent Office during prosecution of a patent (i.e., until a patent issues). This duty exists for “all information known” by the patentee “to be material to patentability,” regardless of how a patentee came to know of the prior art. Disclosing prior art to the Patent office places that information in the public record. If the prior art is strong, this may potentially call into question the validity of not only the pending continuation but also any existing patents and applications.

Evolving Prosecution Laches Defense

“Prosecution laches is an equitable defense to a charge of patent infringement.” An issued patent may be unenforceable due to prosecution laches if there is an “unreasonable and unexplained delay in prosecution that constitutes an egregious misuse of the statutory patent system. . . .”[9] In recent years, courts have increasingly found prosecution laches for these so-called “submarine patents” in cases where a party obtains claims to cover a competitor’s product in a substantially delayed application.[10]

By contrast, the Federal Circuit has also strongly endorsed the use of continuations.

[T]here is nothing improper, illegal or inequitable in filing a patent application for the purpose of obtaining a right to exclude a known competitor’s product from the market; nor is it in any manner improper to amend or insert claims intended to cover a competitor’s product the applicant’s attorney has learned about during the prosecution of a patent application.[11]

This dichotomy shows that prosecution laches is an evolving and somewhat uncertain area of law, which may add some risk to filing continuations.


On balance, the flexibility offered by the ability to obtain new claims with a continuation might outweigh the potential drawbacks, making it a valuable investment for some patentees.

Our team at Dunlap Bennett & Ludwig can help you protect and defend your intellectual property and physical products. To learn about how Dunlap Bennett & Ludwig can assist you with your patent needs, contact us by calling 800-747-9354 or by emailing

[1] MPEP 201.07 Continuation Application, USPTO

[2] Id.

[3] MPEP 201.08 Continuation-in-Part Application, USPTO

[4] MPEP 201.06 Divisional Application, USPTO

[5] Guide to Selling Your Patent & Other Free Resources from Tynax, Tynax Patent Brokers,

[6] Inter Partes Review, USPTO,

[7] IPRs: Balancing Effectiveness vs. Cost, RPX (Jun. 17, 2016),

[8] MPEP 2701 Patent Term, USPTO,

[9] Cancer Research Tech. Ltd. v. Barr Labs., Inc., 625 F.3d 724, 728 (Fed. Cir. 2010) (citations omitted).

[10] E.g.Hyatt v. Hirshfeld, 998 F.3d 1347, 1351 (Fed. Cir. 2021); Personalized Media Communs., LLC v. Apple, Inc., 552 F. Supp. 3d 664, 667 (E.D. Tex. 2021).

[11] Kingsdown Med. Consultants, Ltd. v. Hollister Inc., 863 F.2d 867, 874 (Fed. Cir. 1988).

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Posted in: Intellectual Property, Intellectual Property - Patents

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