A new patent cancellation system has been enacted for patents registered on or after March 1 2017. Previously, non-interested parties were permitted to file an invalidation action against a patent within three months of the patent being registered (interested parties may file an invalidation action at any time). Now, non-interested parties may no longer file invalidation actions, but any party may file a cancellation action against a patent within six months of the patent's publication date.

Grounds for cancellation

The assertable grounds for cancellation are limited to:

  • lack of novelty or inventive step in view of written publications, including patent and non-patent literature (as opposed to public use or knowledge); and
  • violation of the first-to-file rule (eg, the claimed invention was already claimed in an earlier-filed patent application).

Other grounds for invalidation, such as violation of patentable subject matter, are not available in cancellation actions. In addition, a petitioner cannot rely solely on the prior art cited during the prosecution of the patent. The petitioner may request cancellation based on a combination of prior art references cited during prosecution and a new prior art reference, but at least one new prior art reference is needed.

Time limit for petitions

A petition for patent cancellation may be submitted from the date of registration of a patent until six months from the publication of the patent. In contrast, an invalidation action may be initiated at any time after a patent is registered, even after the patent has expired.


Through a panel, the Intellectual Property Trial and Appeal Board (IPTAB) of the South Korean Intellectual Property Office (KIPO) reviews cases based only on documentary examination and then issues a written decision.

After a petition has been submitted, the IPTAB will decide whether to institute substantive proceedings after six months have passed from the patent publication date. Further, the IPTAB will decide whether to institute proceedings only after reviewing all petitions filed against the patent at issue. That is, if multiple petitions are submitted against one patent, the IPTAB will consolidate them into one proceeding and issue one written decision for all petitions at the close of the proceeding.

If the IPTAB determines that at least one of the cancellation grounds has merit, it will issue a notice – including the cancellation grounds – to the patentee. The patentee will then be given a chance to submit its response with a request for correction (proposed post-grant amendment) within a certain period of time.

Although the Patent Act states that the IPTAB will review a case based on documentary examination, the IPTAB's internal regulation on managing hearings and other similar proceedings allows a patentee or petitioner for patent cancellation to request an interview with the IPTAB (generally, the responsible IPTAB examiner). In addition, if the case is complicated, the IPTAB has discretion to hold a technical hearing to ask one or both parties to present their explanations and arguments regarding certain issues. Therefore, it may be strategically advantageous to request an interview or technical hearing if the patent at issue is critical. After the patentee's response, the IPTAB panel will issue a written decision.


If the IPTAB finds that at least one claim of the patent should be cancelled, the patentee may appeal to the Patent Court within 30 days of the receipt of the official copy of the decision, with the KIPO as the defendant (accordingly, at the Patent Court, the case turns into an inter partes proceeding). However, the petitioner cannot appeal if the IPTAB finds the patent valid.

Effect of decisions

The IPTAB renders a written decision on a claim-by-claim basis (ie, finding one claim invalid does not mean that the patent as a whole is cancelled). If a decision to cancel patent claims becomes final and conclusive, the cancelled patent claims are deemed never to have existed. In other words, the cancelled patent claims are retroactively invalid. However, there is no estoppel attached to a decision to uphold the validity of a patent claim. Thus, an invalidation action may be initiated based on the same reference(s). However, in practice, since the IPTAB is responsible for both cancellation and invalidation actions, it would be difficult to obtain a different outcome from the IPTAB in a subsequent invalidation action (particularly based on the same references). Therefore, depending on the importance of the patent and budget constraints, challengers generally should plan to file either a cancellation or an invalidation action, not both.

For further information on this topic please contact John J Kim or Minho Lee at Kim & Chang by telephone (+82 2-3703-1114) or email (jjhkim@kimchang.com or mhlee1@kimchang.com). The Kim & Chang website can be accessed at www.kimchang.com.

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