What Is Patent Prosecution?

Patent prosecution is the process of obtaining a granted patent from a patent office. It refers to the entire back-and-forth between the applicant (or their attorney) and the patent examiner — from filing the application to receiving the final decision. The term has nothing to do with criminal law, despite what the word "prosecution" might suggest.

Think of it as a structured negotiation. The applicant submits claims defining what they want to protect. The examiner reviews those claims against prior art and patentability requirements. The examiner raises objections. The applicant responds with arguments, amendments, or evidence. This cycle continues until the claims are allowed, the application is abandoned, or the applicant appeals.

What Happens During Prosecution

Patent prosecution typically follows this sequence:

Filing. The application is submitted to the patent office with a specification, claims, drawings (if applicable), and filing fees. In some offices (JPO, KIPO), a separate request for examination must also be filed — without it, the application sits unexamined.

Formal examination. The patent office checks that the application meets formal requirements — correct format, proper fees, necessary documents. This is administrative, not substantive.

Publication. In most jurisdictions, the application is published 18 months after the earliest priority date, regardless of whether examination has begun. Publication makes the application part of the public record and establishes it as prior art against later filings.

Substantive examination. An examiner reviews the claims against patentability criteria — novelty, inventive step (non-obviousness), industrial applicability (utility), enablement, and written description. The examiner searches prior art databases and assesses whether the claims meet each criterion.

Office Action. If the examiner finds problems, they issue an Office Action — a formal document identifying the rejections and objections. The applicant typically has 2–6 months to respond, depending on the jurisdiction.

Response. The applicant responds by arguing against the examiner's rejections, amending claims, or both. The goal is to persuade the examiner that the claims are patentable or to narrow them enough to overcome the prior art while retaining commercial value.

Further Office Actions. The cycle may repeat. In the US, a "Final" Office Action can be issued after the first response, though "final" does not mean the end — options remain, including a Request for Continued Examination (RCE), appeal, or examiner interview.

Allowance and grant. When the examiner is satisfied, a Notice of Allowance is issued. The applicant pays the issue fee, and the patent is granted.

How Long Does Prosecution Take?

Prosecution timelines vary significantly by jurisdiction and technology area:

Accelerated examination programmes — such as USPTO Track One, JPO Super Accelerated Examination, and the Patent Prosecution Highway (PPH) — can significantly reduce these timelines.

Key Prosecution Concepts

Broadest reasonable interpretation (BRI): During prosecution, examiners construe claims using the broadest reasonable meaning. This standard is broader than how courts interpret claims in litigation — meaning claims face a tougher test during prosecution.

Prosecution history estoppel: Every statement made during prosecution becomes part of the permanent record. Arguments and amendments that narrow claim scope limit how broadly those claims can be interpreted later, including under the doctrine of equivalents in litigation.

Duty of candor (US): US applicants and their attorneys have a legal duty to disclose material prior art known to them. Failure to disclose can render the entire patent unenforceable through an inequitable conduct defence.

Examiner interviews: Most patent offices allow the applicant's attorney to speak directly with the examiner — by phone or in person — to discuss rejections. Interviews are one of the most effective prosecution tools and are significantly underused by applicants.

Sources

1. MPEP — Manual of Patent Examining Procedure — Comprehensive USPTO guidance on all aspects of patent prosecution
2. EPO Guidelines for Examination — European examination procedures and standards
3. USPTO Track One Prioritized Examination — Accelerated US prosecution programme
4. USPTO Patent Prosecution Highway (PPH) — Inter-office accelerated examination programme
5. JPO Patent Examination — Japan Patent Office examination procedures