A granted Korean patent enjoys a strong presumption of validity, but recent data shows that presumption is far from bulletproof. Patent invalidation trials in Korea succeed in roughly half of all cases. When infringement disputes start, the alleged infringer's first move is usually an invalidation petition, and the trial outcome often dictates whether the parallel infringement suit can move at all.
This guide explains who can file an invalidation trial, on what grounds, through what procedure, and how the post-decision rights look — written from a practitioner's perspective. Beyond infringement defence, invalidation is also a tool for clearing senior patents that block your own product launch.
What Is a Patent Invalidation Trial?
An invalidation trial under Patent Act article 133 is an inter partes procedure to wipe out a granted patent that suffers from a statutory defect. Unlike refusal-decision appeals, which fight examination outcomes, invalidation trials attack rights that are already on the register. The petitioner and the patentee exchange briefs and evidence in an adversarial format before a panel at the Korean IPTAB.
Per KIPO's procedural guide, invalidation can be sought claim by claim and even after the patent has expired. The post-expiration option exists because past damages claims based on the patent can still be defeated by a later invalidation, retroactively.
Standing — Interested Parties and Examiners
Article 133(1) limits standing to interested parties and to KIPO examiners. An interested party is someone whose business is directly affected by the patent — a competitor in the same field, a recipient of an infringement warning, or an applicant whose own patent was rejected over the target. Generic curiosity is not enough; petitions normally include business documents, warning letters, or office actions to prove the nexus.
Common Invalidity Grounds
Article 133(1) lists a wide range of grounds, but in practice the bulk of cases turn on a handful. Lack of inventive step (Patent Act article 29(2)) is the most common single ground, and specification-disclosure issues under article 42 also feature prominently. Petitions usually combine several grounds claim-by-claim.
- Lack of novelty — public knowledge, public use, or printed publication before filing (art. 29(1))
- Lack of inventive step — easily inventable by a person of ordinary skill (art. 29(2))
- Insufficient disclosure or unclear claims (art. 42(3)(4))
- Conflict with an enlarged prior application (art. 29(3))
- Lack of inventorship or right to apply (art. 33 etc.)
- Improper amendment that effectively broadened the claim scope (art. 136)
Procedure at a Glance
The basic flow is petition, answer, briefing and evidence, then decision. Patentees can file a claim-amendment request during the trial to narrow claims and avoid the asserted grounds. Each amendment triggers fresh briefing rounds, so cases run longer when amendments cycle. Average disposition time is 12-18 months depending on complexity and the number of amendment rounds.
| Step | Party | Timing |
|---|---|---|
| File petition | Petitioner | Available even after the patent expires |
| File answer | Patentee | Usually 30 days (extendable) |
| Claim amendment request | Patentee | Within the answer period |
| Supplemental briefs and evidence | Both parties | Multiple rounds during trial |
| Decision | IPTAB panel | Average 12-18 months |
| Service of decision | IPTAB | Appeal due within 30 days of service |
Effect of the Decision and Appeal
A final invalidation decision treats the patent as never having existed (Patent Act article 133(3)). Past infringement injunctions and damages awards based on it become candidates for unjust enrichment claims and retrials. Appeals run to the Patent Court within 30 days of service, then up to the Supreme Court — same path as in other administrative trials.
- Final invalidation effect
- Void ab initio Patent Act art. 133(3) — retroactive
- Effect on infringement judgments
- Retrial ground Even final infringement judgments may be retried
- Past damages payments
- May be recovered as unjust enrichment Fact-dependent
- Appeal window
- 30 days from service Patent Court action
Recent Statistics — About Half Succeed
Recent reports place Korea's industrial-property invalidation success rate around 50% over the past five years, with patents at roughly 50%, designs at 57.8%, trademarks at 44.6%, and utility models at 25%. The Korean rate sits well above the United States PTAB (around 25.6% over 2012-2022) and Japan's JPO (around 11.5% in 2023), making Korea a comparatively friendly forum for invalidation petitioners source.
| Jurisdiction | Recent invalidation rate (approx.) | Note |
|---|---|---|
| Korea | ~50% | Patents, utility models, designs, trademarks |
| US PTAB | ~25.6% | 2012-2022 cumulative |
| Japan JPO | ~11.5% | 2023 invalidation trials |
Cost and Timeline: A Practitioner's View
KIPO official fees scale with the number of claims and start in the low six-figure won range. Attorney fees vary widely with complexity, the volume of foreign-language prior art, and the number of amendment rounds. In some cases, prior-art search and translation costs from US or European sources approach the main attorney fee in size.
Frequently Asked Questions
Q1. Why bother with invalidation after a patent has expired?
Past damages claims based on the patent stay alive after expiration. A later invalidation retroactively defeats them, which is the main practical reason to keep filing post-expiration. The decision can also weaken citations of the patent in unrelated examination histories where it appeared as prior art.
Q2. How does invalidation interact with infringement litigation?
The two run on separate tracks, but Korean infringement courts can independently assess whether invalidity is 'manifest' and limit the patentee's enforcement (the abuse-of-rights defence). The standard playbook for accused infringers is to file invalidation in parallel and run both tracks. A final invalidation typically settles the infringement case.
Q3. Can some claims be invalidated while others survive?
Yes — claims are tried separately, and partial invalidation is common. Petitioners normally target the claim that most directly reads on the accused product, while patentees use amendment requests to surrender peripheral claims to save the core. Plan claim-by-claim from the start.
Q4. Can foreign prior art be used in a Korean invalidation trial?
Yes. The Korean Patent Act recognises prior art that was publicly known, used, or published 'inside or outside Korea' before the filing date. Foreign-language references must be filed with reliable translations, and supporting evidence (database extracts, notarised pages) helps prove the publication date and authenticity.
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