How an Ex Parte Reexamination Works, Step by Step

An ex parte reexamination is a USPTO proceeding to reassess the patentability of one or more claims of an issued patent, based on prior art that raises a substantial new question. Any person may file. The procedure runs between the USPTO and the patent owner, there is no formal inter partes participation by a third-party requester after the request is filed. This is a step-by-step walkthrough of how a reexam moves from request to certificate.

Who can file

Under 35 U.S.C. 302, any person may file a request for ex parte reexamination at any time during the period of enforceability of a patent. Patent owners file (typically to strengthen claims pre-litigation, or to address newly discovered prior art). Third parties file too, most commonly accused infringers or licensees seeking to invalidate a patent at lower cost than litigation. Third-party requesters may file anonymously through a representative.

The request

The request must identify the claims being challenged, the prior art being relied on, and an explanation of how the prior art raises a substantial new question of patentability for each challenged claim. The required statutory fee applies.

The request is the only formal participation a third-party requester gets in the procedure. After SNQ is granted, the reexamination runs between the USPTO and the patent owner.

SNQ determination

Within three months of the filing date, the USPTO determines whether the request raises a substantial new question (SNQ) under 35 U.S.C. 303(a). The standard asks two things: is the question new (not previously considered in the patent's prosecution), and is it substantial (would a reasonable examiner consider the prior art important to the patentability of any claim). (Deeper on the SNQ standard.)

Across the 4,500+ utility-patent ex parte reexaminations since 2012, roughly 95% of requests have been granted SNQ. The procedural gate is real but rarely closed. Denials concentrate on two grounds: cumulativeness (the references were considered during prosecution) and technical insufficiency (the references do not actually disclose what the request claims).

Patent owner statement

If SNQ is granted, the USPTO issues an order for reexamination. The patent owner may file a statement under 37 CFR 1.530 within two months, addressing the prior art and proposing any claim amendments. If a patent owner statement is filed, the third-party requester (if any) gets one chance to reply within two months under 37 CFR 1.535.

Many patent owners skip the statement and address the prior art directly through the office action sequence. Filing a statement triggers the requester's reply right; skipping it forecloses any further requester participation.

Examination

A reexamination examiner, assigned from the roughly 110 active USPTO reexam examiners, issues an initial office action on the merits, typically several months after the order. Rejections may be on 102, 103, 112, or other grounds. (Who these examiners are and how they vary.)

On average, reexams generate 1.5 office actions before final disposition. About a third of cases close after a single office action. The remainder run through one or two follow-on actions. Average pendency from filing to final disposition is 17.4 months.

The patent owner may amend claims to overcome rejections but cannot broaden them. 35 U.S.C. 305 statutorily bars any amendment that enlarges the scope of an original claim. This is one of the defining constraints of the procedure: the only direction claims can move is narrower.

Final disposition

A reexamination ends in one of three ways:

1. Reexamination certificate. The USPTO issues a certificate confirming, amending, canceling, and (if any) newly adding claims. Across closed cases, 94% close this way.
2. SNQ denial. Roughly 5% of requests are denied at the SNQ determination stage and never reach the merits.
3. Other termination. A small residual (approximately 1%) terminates for procedural reasons such as concurrent reissue, patent expiration, or fee defaults.

Appeals

The patent owner may appeal a final rejection to the Patent Trial and Appeal Board under 35 U.S.C. 134(b). Across closed reexams, about 24% reach the PTAB. From the PTAB, either side may appeal to the Federal Circuit under 35 U.S.C. 141.

PTAB appeals add roughly 12 to 18 months to total pendency on average. CAFC review, when invoked, adds another year.

What the procedure rewards

The structure of an ex parte reexam rewards two things: prior art that is genuinely new relative to prosecution, and arguments that work within the SNQ framework rather than against it. Most of the procedural variance is decided at the SNQ gate and the first office action. Practitioners who treat those two milestones as the load-bearing events of the procedure consistently outperform those who run a generic invalidity playbook.