ReexaminationPost-grantValidity

Reexamination: reopening a granted patent

By Ipiry TeamPublished August 31, 20269 min read

Short answer

Reexamination lets the USPTO re-examine an issued patent against prior art. Two types remain: ex parte reexamination, which anyone can request at any time based on patents and printed publications, and supplemental examination, available only to the patent owner. Reexamination costs far less than a PTAB trial and carries no estoppel for the requester, but the requester has no participation after filing and the patent owner can amend claims.

Reexamination reopens prosecution on a patent that has already granted.

An examiner looks at the claims again, against prior art the Office may not have considered properly the first time.

Two types survive. Ex parte reexamination, which anyone can request, and supplemental examination, which only the patent owner can use.

Inter partes reexamination is gone, replaced by inter partes review in 2012 — which is why older material describing three types is out of date.

The two surviving types

	Ex parte reexamination	Supplemental examination
Who can request	Anyone, including anonymously	Patent owner only
Grounds	§102/§103 on patents and printed publications	Any information
Purpose	Challenge or strengthen	Address inequitable conduct exposure
Requester participation	Minimal	N/A
Estoppel on the requester	None	N/A
Can amend claims	Patent owner can, narrowing only	Yes, if reexamination is ordered

Ex parte reexamination is the challenge route. Supplemental examination is a patent owner's cleanup tool. See ex parte reexamination.

What happened to inter partes reexamination

	Inter partes reexamination	Replaced by
Existed	Until September 2012	Inter partes review
Forum	Examiner	PTAB
Requester participation	Limited but real	Full party
Timetable	None	Statutory

Older material describing three reexamination types is out of date. Inter partes reexamination was phased out by the America Invents Act, and requests could no longer be filed after September 2012.

Inter partes review replaced it with a better-designed procedure — a real adversarial trial before administrative patent judges, on a fixed timetable. See inter partes review.

The substantial new question standard

The threshold for ordering reexamination at all.

Requirement	Detail
A question about patentability	Raised by patents or printed publications
New	Not already considered in the same way
Substantial	A reasonable examiner would consider it important
Previously cited art	Can still qualify if presented in a new light

Previously considered art is not automatically excluded. A reference the examiner cited but applied differently can support a substantial new question if the request shows it teaches something not previously appreciated.

The standard is lower than the PTAB's institution threshold, which requires a reasonable likelihood of prevailing. Reexamination is ordered more readily than inter partes review is instituted.

Reexamination versus PTAB trials

	Ex parte reexamination	Inter partes review
Forum	Examiner	PTAB, three judges
Requester participation	Almost none	Full party
Cost	Much lower	Significant
Timetable	Ordinary examination pace	Statutory, ~18 months
Estoppel	None	Yes on a final written decision
Anonymity	Available	No
Deadline after being sued	None	1 year from service
Claim amendment by owner	Readily available	Motion to amend, rarely granted
Standard	Preponderance	Preponderance

The two big trade-offs are participation and estoppel. IPR gives you a seat at the table and takes your documentary invalidity case; reexamination gives you neither.

Amendment availability cuts against the challenger in reexamination. The patent owner can narrow claims through ordinary prosecution, which may produce a valid patent that still reads on the accused product.

Why anonymity matters

Situation	Benefit
Challenging without revealing interest	Available in ex parte reexamination
Avoiding a declaratory judgment counterclaim	Possible
Not signalling a product launch	Possible
Outside the one-year IPR bar	Reexamination has no equivalent bar

A party barred from IPR by the one-year rule can still file a reexamination request, which is one of the main practical reasons the route survives.

Anonymity is genuine but not absolute. A request must be filed by someone, and the surrounding circumstances frequently make the interested party obvious.

The patent owner's use

Requesting reexamination of your own patent sounds odd and is a real strategy.

Goal	How it works
Strengthen before asserting	Surviving the best prior art makes later challenges harder
Address art found late	Get it considered rather than leaving it hanging
Fix a known weakness	Amend narrowly and deliberately
Supplemental examination	Remove inequitable conduct exposure

The risk is real. Claims can be narrowed or cancelled, and the process is not controllable once ordered.

But a patent that has survived reexamination over strong art is materially harder to attack. An accused party has to find something the Office has now considered twice.

Supplemental examination specifically

Feature	Detail
Who	Patent owner only
Purpose	Have the Office consider information relevant to patentability
Effect if the patent survives	That information generally cannot support inequitable conduct
Grounds	Any information, not just patents and publications
Outcome	May lead to ex parte reexamination being ordered

It exists to address the inequitable conduct problem. A patent holder who discovers material art that should have been disclosed during prosecution faces potential unenforceability of the entire patent — a far worse outcome than narrower claims.

Supplemental examination converts that risk into a narrower question. Submit the information, let the Office consider it, and the unenforceability argument is largely removed if the patent survives.

It is not a complete shield. It does not protect against conduct already pleaded in litigation, and it must be used before the issue arises.

What can and cannot be raised

Ground	Ex parte reexamination
§102 anticipation, on documents	Yes
§103 obviousness, on documents	Yes
Prior public use	No
On-sale activity	No
§101 eligibility	No
§112 enablement or definiteness	No
Inequitable conduct	No

The documentary limitation matches inter partes review. Both are confined to patents and printed publications, which is why the choice between them turns on process rather than grounds.

Grounds outside that set stay in district court, where any invalidity theory is available at the clear and convincing standard. See patent invalidation.

Worked example: choosing the route

A company sued 14 months ago, holding two printed publications.

Option	Available?	Why
Inter partes review	No	One-year bar passed
Post-grant review	No	Well outside the nine-month window
Ex parte reexamination	Yes	No deadline
District court invalidity defence	Yes	Clear and convincing standard

What reexamination offered

Factor	Assessment
Cost	A fraction of the litigation validity fight
Standard	Preponderance, better than court
Estoppel	None — defence preserved in court
Participation	Almost none — a genuine drawback
Amendment risk	Patent owner may narrow to something still infringed
Stay prospects	Weaker than with an instituted IPR

The one-year bar drove the decision. Having missed the IPR window, reexamination was the only route to the preponderance standard.

No estoppel meant the district court defence stayed intact, so the request cost nothing strategically even if it failed.

The amendment risk was the real concern. If the owner narrowed the claims to distinguish the references while still covering the product, the reexamination would have strengthened the patent rather than defeating it.

Concurrent proceedings

Situation	Effect
Reexamination alongside district court litigation	Court may stay, less readily than for IPR
Reexamination alongside an IPR	Board may address the overlap
Two reexaminations on one patent	May be merged
Reissue and reexamination together	Frequently merged

Stays are harder to obtain than with an instituted IPR, because reexamination has no statutory end date and a court cannot predict when it will conclude.

Merger is common where proceedings overlap, and it can extend timelines further.

Outcomes

Outcome	Meaning
Certificate confirming claims	Claims survive unchanged — patent is stronger
Certificate with amended claims	Narrower claims, intervening rights may apply
Certificate cancelling claims	Those claims are gone
Mixed	Common — some confirmed, some amended, some cancelled

Intervening rights matter after amendment. A party who began practising the invention before the amended claims issued may have rights that limit enforcement against them.

Confirmation is a real risk for a challenger. A patent that emerges confirmed is harder to attack afterwards than it was before the request.

Fees and cost profile

Item	Note
USPTO request fee	Substantial, non-refundable
Preparing the request	The main cost
Requester's ongoing costs	Essentially none after filing
Patent owner's costs	Ongoing, through prosecution

The cost asymmetry runs the other way here. A challenger's spending stops at filing; the patent owner then funds a full prosecution cycle.

That is a real strategic feature, distinct from the merits, and it is one reason reexamination is used against owners with limited resources.

Timing

Stage	Nature
Request filed	With fee and a statement of the SNQ
Order or denial	Within about three months
Patent owner statement	Optional
Requester reply	Only if the owner filed a statement
Examination	Ordinary office action and response cycles
Certificate issues	When prosecution concludes

There is no statutory deadline for completion, which is the main structural difference from a PTAB trial. Reexamination follows ordinary examination pace and can run considerably longer than eighteen months.

That unpredictability weakens stay applications. A court asked to stay litigation pending a proceeding with no end date is less likely to grant it.

Reissue: the adjacent procedure

	Reexamination	Reissue
Who files	Anyone, or the owner	Owner only
Purpose	Test validity over prior art	Correct a defective patent
Can broaden claims	No	Yes, within 2 years of grant
Can narrow claims	Yes	Yes
Replaces the original	No — certificate issues	Yes

Reissue is the only route to broader claims after grant, and the two-year window for broadening is strict.

The two are frequently confused because both reopen an issued patent, but their purposes are opposite: one tests validity, the other fixes errors.

Reexamination: the checklist

Check whether you are inside the IPR one-year bar first. If you are, compare both routes properly.
Confirm your grounds are documentary. Only patents and printed publications qualify.
Frame a substantial new question, and remember previously cited art can qualify if presented in a new light.
Weigh estoppel heavily. Reexamination creates none for the requester; IPR does.
Accept that you will not participate after the initial exchange.
Model the amendment risk. A narrowed but valid patent may still cover your product.
Consider anonymity if revealing your interest would trigger a counterclaim or signal a launch.
As a patent owner, consider requesting it yourself before asserting, to strengthen the patent.
Use supplemental examination where undisclosed material art creates inequitable conduct exposure.
Expect no fixed timetable, and factor that into any stay application.

Common questions

What is patent reexamination?

A USPTO procedure in which an examiner re-examines the claims of an issued patent against prior art. It reopens prosecution on a granted patent and can result in claims being confirmed, amended or cancelled. Two types remain available: ex parte reexamination and supplemental examination.

What types of reexamination exist?

Ex parte reexamination, which anyone including the patent owner can request, and supplemental examination, which only the patent owner can request. Inter partes reexamination was replaced by inter partes review under the America Invents Act in 2012.

What is a substantial new question of patentability?

The threshold for ordering reexamination. The request must raise a question the Office has not already considered in a way that a reasonable examiner would regard as important in deciding whether the claims are patentable. Previously considered art can qualify if presented in a new light.

Who can request reexamination?

Anyone, for ex parte reexamination, including the patent owner and anonymous third parties. Supplemental examination is limited to the patent owner. The ability to file anonymously is one reason ex parte reexamination is still used despite its limitations.

What grounds can reexamination address?

Only patents and printed publications, under §102 and §103. Prior public use, on-sale activity, §101 eligibility and §112 problems cannot be raised in ex parte reexamination. Supplemental examination is broader and can address any information.

Does reexamination create estoppel?

Ex parte reexamination creates no estoppel against a third-party requester in later litigation, which is a significant advantage over inter partes review. The requester does keep the ability to raise the same or other grounds elsewhere.

Can the requester participate?

Barely. In ex parte reexamination the third-party requester files the request and may reply once to the patent owner's initial statement, then has no further involvement. The rest proceeds between the examiner and the patent owner.

Why would a patent owner request reexamination of their own patent?

To strengthen a patent before asserting it. Surviving reexamination over the best prior art the owner could find makes the patent harder to challenge later. It is a deliberate strategy, though it carries the risk of losing claims.

What is supplemental examination?

A procedure allowing a patent owner to have the Office consider information that might otherwise support an inequitable conduct allegation. If the information is considered and the patent survives, it generally cannot later be used to hold the patent unenforceable on that basis.

How long does reexamination take?

Longer than a PTAB trial in many cases, because it follows ordinary examination procedure with office actions and responses rather than a statutory timetable. There is no one-year deadline equivalent to the PTAB's.

Can claims be broadened in reexamination?

No. Claims may be confirmed, amended or cancelled, but not broadened. Amendments must narrow. Broadening after grant is available only through reissue, and only within two years of the original grant.

Should I use reexamination or inter partes review?

IPR if you want to participate, want a fixed timetable and can accept estoppel. Reexamination if you want lower cost, anonymity, no estoppel, or if you are outside the one-year bar. The choice usually turns on estoppel and participation.

Ex parte reexamination

How ex parte reexamination works — who can file, the substantial new question standard, the limited requester role, why there is no estoppel, and when it beats an IPR.

Inter partes review: what an IPR is and when to file one

IPR is the PTAB proceeding to cancel patent claims over prior art. The one-year bar, the institution decision, what estoppel costs you, and why institution rates have collapsed.

Patent invalidation: the routes and what each costs

Four routes to invalidate a patent — IPR, PGR, ex parte reexamination and district court. Which grounds each allows, what the burden is, and what estoppel you take on.

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