Brief summary
- In Korea, one patent application is filed for each invention. A group of inventions that forms a single general inventive concept can be filed in one application (Patent Act (특허법), Art. 45).
- Article 6 of the Enforcement Decree of the Patent Act (특허법 시행령) sets two requirements for a group of inventions. The first is a technical correlation among the claimed inventions. The second is the same or corresponding technical features that are an improvement over the prior art.
- Lack of unity is a ground for rejection (Patent Act, Art. 62, subparagraph 4). It is not among the grounds for a trial for invalidation (Art. 133(1)).
- The examiner raises lack of unity in a notice of grounds for rejection. The applicant responds by amendment or by a divisional application.
This article is based on the Patent Act in force from 11 November 2025, the Enforcement Decree of the Patent Act in force from 1 October 2025 and the Patent Examination Guidelines (특허·실용신안 심사기준) in force from 13 March 2026. Last verified on 9 October 2026.
Last verified
The unity rules at a glance
| Item | Content | Basis |
|---|---|---|
| Principle | One patent application for each invention | Patent Act, Art. 45(1), main clause |
| Exception | A group of inventions that forms a single general inventive concept can be filed in one application | Patent Act, Art. 45(1), proviso |
| Requirement 1 | A technical correlation among the claimed inventions | Enforcement Decree, Art. 6, subparagraph 1 |
| Requirement 2 | The same or corresponding technical features. The features must be an improvement over the prior art, with each invention considered as a whole | Enforcement Decree, Art. 6, subparagraph 2 |
| Effect during examination | Ground for rejection. A notice of grounds for rejection and an opportunity to file a written argument | Patent Act, Art. 62, subparagraph 4, and Art. 63(1) |
| After registration | Not a ground for a trial for invalidation or for a request for revocation of a granted patent | Patent Act, Art. 133(1) and Art. 132-2(1) |
| Provision of information by a third party | Not possible on the ground of a violation of Art. 45 | Patent Act, Art. 63-2, proviso |
| Period for a divisional application | The period in which amendment is possible, three months from service of the certified copy of the decision of rejection, and three months from service of the certified copy of the decision to grant | Patent Act, Art. 52(1) |
“Unity of invention” (발명의 단일성) is not a term used in the text of the Patent Act or the Enforcement Decree. It is the short name that the Examination Guidelines of the Ministry of Intellectual Property (지식재산처) give to the requirement of Art. 45. [3]
The test is the same or corresponding technical features that improve on the prior art
The Korean test for unity is whether the claimed inventions have the same or corresponding technical features. Those technical features must be an improvement over the prior art (Enforcement Decree of the Patent Act, Art. 6, subparagraph 2). [2] Article 45(1) of the Patent Act sets the principle of one patent application for each invention. [1] The proviso to the same paragraph allows a group of inventions that forms a single general inventive concept to be filed in one application. [1]
The requirements are in Article 6 of the Enforcement Decree. Subparagraph 1 requires a technical correlation among the claimed inventions. [2] Subparagraph 2 requires the claimed inventions to have the same or corresponding technical features. [2] The technical features of subparagraph 2 must be an improvement over the prior art, with each invention considered as a whole. [2] Both requirements must be met. [2]
The Examination Guidelines call the feature of subparagraph 2 a “special technical feature”. The Guidelines describe it as the improved part that distinguishes each invention, considered as a whole, from the prior art. [3] Special technical features do not have to be the same. It is enough that they correspond. The Guidelines give the example of a spring in one claim and a rubber block in another claim. [3]
The assessment does not depend on the form of the claims. The same test applies whether the inventions are in separate claims or are written as alternatives within one claim. [3] Several independent claims in the same category can be a group of inventions, and so can several independent claims in different categories. [3]
The current text of Art. 45 was wholly amended by Act No. 12753, which took effect on 1 January 2015. The previous provision applies to patent applications filed before that date (Addenda, Art. 8). [1] The previous Art. 45 also had the principle of one application for one invention and the same proviso. [9] Article 6 of the Enforcement Decree has not changed since it was wholly amended on 13 June 2003. [2] The text of Art. 45 is also the same in the amended Patent Act (Act No. 21955) scheduled to take effect on 16 March 2027. [5]
Unity is assessed again after the prior art search
Claims that shared a common feature at filing can lose unity when prior art is found. The Examination Guidelines state that unity can be assessed before the prior art search. However, they state that it is generally assessed after the prior art has been taken into account. [3]
The example in the Guidelines is an application that claims A+X and A+Y. Before the search, A is common, so unity can be considered to exist. If prior art for A is found, the two claims no longer have the same or corresponding special technical features. The Guidelines state that unity is then lacking. [3]
In principle, unity does not need to be assessed between an independent claim and its dependent claims. [3] The exception is when the independent claim lacks novelty or inventive step over the prior art. The Guidelines state that a unity problem can then arise among the claims that refer to that independent claim. [3]
The Guidelines give an example with one independent claim and four dependent claims. [3]
| Claim | Elements | Explanation in the Guidelines | Group assigned in the Guidelines |
|---|---|---|---|
| 1 (independent) | A | A is in the prior art | Group 1 |
| 2 | A+B | A+B is in the prior art. No special technical feature | Group 1 |
| 3 | A+C | C is not in the prior art. The special technical feature is C | Group 2 |
| 4 | A+C+D | The special technical feature is C | Group 2 |
| 5 | A+F | F is not in the prior art. The special technical feature is F | Group 3 |
In this example, C and F are not the same or corresponding features. Claim 1 is placed in the same group as claim 2. The examiner can point out that there are three groups of inventions and issue a notice of grounds for rejection for lack of unity. The examiner then also notifies the result of the novelty and inventive step examination of Group 1. [3]
The Guidelines deal with some relationships separately. Unity between a product and a process for manufacturing that product is assessed by whether the process is suitable for manufacturing the product. [3] A Markush-type claim satisfies unity if the alternative elements have a similar nature or function. [3]
The examiner examines at least one group and issues a notice of grounds for rejection
When an application lacks unity, the examiner in principle assesses the requirements for patentability for at least one group of inventions. The ground for rejection for lack of unity is notified for all the claims. [3] Grounds for rejection found in that one group are notified at the same time as the ground for rejection under Art. 45. [3]
The group to be examined is determined on the basis of the “first invention”. In the Guidelines, the first invention means the main invention and is not related to the order of the claims. [3] An invention that can be examined without additional effort, such as an invention that differs only in category, can be included in the inventions subject to examination. [3] Inventions that do not belong to the examined group can be excluded from the prior art search (Examination Guidelines, Part 5, Chapter 2, 3.2). [3]
If the examiner finds it necessary for the efficient progress of examination, the examiner can first notify only the violation of Art. 45. [3] In that case, the “Considerations of Amendment” (참고사항) section of the notice states that the requirements for patentability have not been examined for all the claims. [3]
A lack of unity does not always lead to a notice on that ground. The Guidelines refer to cases in which examination can be completed without further searching. One example is when the prior art already found is enough to deny the novelty or inventive step of all the claims. [3]
Failure to meet the requirement of Art. 45 is a ground for rejection under Art. 62, subparagraph 4, of the Patent Act. [1] The examiner notifies the grounds for rejection before issuing a decision of rejection (decision to reject a patent application). The examiner must set a period and give the applicant an opportunity to file a written argument (Art. 63(1)). [1]
The response is an amendment or a divisional application
Within the period for submission of a written argument, the applicant can amend the claims or move some of the inventions to a divisional application. An applicant who has received a notice of grounds for rejection for the first time can amend the specification or drawings within that period for submission of a written argument (Patent Act, Art. 47(1), subparagraph 1). [1] An amendment must stay within the matter described in the specification or drawings originally attached to the application (Art. 47(2)). [1]
There are further limits when the applicant has received a notice of a ground for rejection that arose from an amendment, or requests re-examination. In those cases, the claims can be amended only in the cases listed in the subparagraphs of Art. 47(3), such as narrowing the claims. [1]
A divisional application can be filed when two or more inventions have been included in one patent application. Its scope is the matter described in the original specification or drawings of the original application (parent application) (Art. 52(1)). [1] There are three periods in which a divisional application can be filed. [1]
| Period | Basis | Scope of application and conditions |
|---|---|---|
| The period in which amendment is possible under Art. 47(1) | Art. 52(1), subparagraph 1 | After a notice of grounds for rejection, the periods set in the subparagraphs of Art. 47(1) |
| Three months from service of the certified copy of the decision of rejection. If the period for filing a petition for trial is extended, the extended period | Art. 52(1), subparagraph 2 | Applications for which the certified copy of the decision of rejection is served on or after 20 April 2022 |
| Three months from service of the certified copy of the decision to grant. If the date when the applicant intends to have the grant of the patent registered is earlier, until that date | Art. 52(1), subparagraph 3 | Applications for which the certified copy of the decision to grant is served on or after 29 July 2015 |
The scope of application in the second row is set in the Addenda to Act No. 18505, Art. 3(1). The scope of application in the third row is set in the Addenda to Act No. 13096, Art. 2(2). [1] The period in the third row is the same when the applicant is served with the certified copy of a trial decision to revoke a decision of rejection, limited to a trial decision made to register a patent. [1]
A patent application in a foreign language can be divided only after the Korean translation has been filed (Art. 52(1), proviso). [1] A divisional application is deemed filed at the time the original application was filed. However, the time of filing the divisional application is used when the provisions listed in the subparagraphs of Art. 52(2) are applied. [1] Examination of a divisional application can be requested even after the period for requesting examination of the original application has expired. The time limit is 30 days from the date of filing the divisional application (Art. 59(3)). [1]
The Guidelines state that the examiner can suggest division when notifying a ground for rejection under Art. 45. [3] Amendments also need care. Deleting the independent claim that served as the basis, or changing the content of the invention, can raise a new unity problem. [3]
If the grounds for rejection are not overcome, the examiner issues a decision of rejection (Art. 62). [1] An applicant who is served with the certified copy of the decision of rejection can request re-examination within three months from the date of service. If the period for filing a petition for trial is extended, the request can be made within the extended period. Re-examination is requested by amending the specification or drawings (Art. 67-2(1)). [1] Re-examination cannot be requested if a decision following re-examination has already been issued or if an appeal against the examiner’s decision to reject a patent application (trial on rulings rejecting patent applications) has been filed. Re-examination also cannot be requested for a separational application (splitting-off) (분리출원). [1] This three-month period applies to applications for which the certified copy of the decision of rejection is served on or after 20 April 2022 (Addenda to Act No. 18505, Art. 7). [1]
The periods for a divisional application are covered separately in this series, in “When can I file a divisional application in Korea?“.
Lack of unity is not a ground for invalidation
Lack of unity is not a ground for invalidating a registered patent. The subparagraphs of Art. 133(1) of the Patent Act list the grounds on which a trial for invalidation can be requested. Article 45 is not among them. [1] The Examination Guidelines also state that the unity requirement is a ground for rejection but not a ground for invalidation. [3]
The previous Art. 133(1) applies to patent rights for which registration of the grant of a patent (registration of establishment of a patent right) was made before 1 March 2017 (Addenda to Act No. 14035, Art. 21). [1] Article 45 is also absent from the subparagraphs of Art. 133(1) in the version in force from 29 July 2015 and in the version in force from 1 July 2014. [9]
The other routes for challenging lack of unity are also closed.
| Procedure | Can it be based on a violation of Art. 45? | Basis |
|---|---|---|
| Provision of information by a third party | No | Patent Act, Art. 63-2, proviso |
| Ex officio re-examination after a decision to grant | Not carried out | Patent Act, Art. 66-3(1), subparagraph 1 |
| Request for revocation of a granted patent | Not among the grounds for the request | Patent Act, Art. 132-2(1) |
| Trial for invalidation | Not among the grounds for the request | Patent Act, Art. 133(1) |
The provision on ex officio re-examination applies to applications for which the decision to grant is made on or after 1 March 2017. The provision on the request for revocation of a granted patent applies to patent rights registered on or after the same date (Addenda to Act No. 14035, Arts. 6 and 10). [1]
How Korea differs
In Korean national examination, lack of unity is handled by a notice of grounds for rejection. The procedure differs from the further search fee in Europe and the restriction requirement in the United States. Article 6, subparagraph 2, of the Enforcement Decree of the Patent Act sets “the same or corresponding technical features” as the requirement. [2] PCT Rule 13.2 and EPC Rule 44(1) set “the same or corresponding special technical features” as the requirement. [6][7]
| System | Test | Procedure when unity is lacking |
|---|---|---|
| Korea (national examination) | The same or corresponding technical features that are an improvement over the prior art (Enforcement Decree, Art. 6) | Notice of grounds for rejection. Amendment or divisional application [1][3] |
| PCT | The same or corresponding special technical features (Rule 13.2) [6] | When the Ministry of Intellectual Property is the International Searching Authority, an invitation to pay additional fees (Enforcement Rules, Art. 106-14) [4] |
| Europe (European search at the EPO) | The same or corresponding special technical features (EPC Rule 44(1)) [7] | Partial search report. A further search fee for each invention within two months (Rule 64(1)) [7] |
| United States | Independent and distinct inventions (37 CFR 1.141(a)). The unity standard for PCT national stage applications (37 CFR 1.475) [8] | Restriction requirement. The applicant elects one invention (37 CFR 1.142, 1.499) [8] |
In the United States, the examiner uses a restriction requirement to make the applicant elect one invention. Claims to the inventions that are not elected are withdrawn from further consideration by the examiner even if they are not cancelled (37 CFR 1.142). [8] The United States also applies the unity standard to PCT national stage applications (37 CFR 1.475). In that case too, the examiner can require the election of an invention (37 CFR 1.499). [8]
In Europe, the EPO draws up a partial search report on the invention first mentioned in the claims. For the European search report to cover the other inventions, a further search fee must be paid for each invention within two months (EPC Rule 64(1)). [7]
In Korean national examination, lack of unity arrives as a notice of grounds for rejection (Patent Act, Art. 62, subparagraph 4, and Art. 63(1)). [1] Under the Examination Guidelines, the examiner selects the invention subject to examination on the basis of the first invention (Part 2, Chapter 5, 4.(5)). [3] Inventions that do not belong to the examined group can be excluded from the prior art search. [3]
The invitation to pay additional fees in Art. 106-14 of the Enforcement Rules of the Patent Act (특허법 시행규칙) is a provision on the international search of an international application. [4] If an international application for which the Ministry of Intellectual Property is the International Searching Authority does not meet the unity requirement, the examiner invites payment of additional fees. [4] If they are not paid, the international search report is limited to the invention, or the group of inventions, first mentioned in the claims (Enforcement Rules, Art. 106-14(3)). [4]
The partial search report of EPC Rule 64(1) relates to the invention first mentioned in the claims. [7] The first invention in the Korean Examination Guidelines is the main invention and is not related to the order of the claims. [3]
What applicants should do
- In general, when a notice of grounds for rejection is received, we suggest first checking the groups of inventions identified by the examiner and the group that was actually examined. Check also whether the “Considerations of Amendment” section states that the requirements for patentability were not examined.
- When the independent claim has been denied over the prior art, we suggest building the amendment around the features that the dependent claims share. The groups of inventions that remain depend on which feature is added to the independent claim.
- For claims deleted by amendment, we suggest deciding at the same time whether to file a divisional application. The periods for a divisional application are fixed by law.
- When a claim set written for the United States or Europe is filed in Korea as it is, it is worth checking in advance the features that the independent claims share. In Korea, lack of unity is notified as a ground for rejection.
- The response in an individual case should be confirmed with a Korean agent.
FAQ
Does Korea have a procedure like the US restriction requirement?
In Korean national examination, lack of unity is a ground for rejection under Art. 62, subparagraph 4, of the Patent Act. [1] The examiner raises it in a notice of grounds for rejection, and the applicant responds within the period for submission of a written argument by amendment or by a divisional application. [1][3] Under the Examination Guidelines, the examiner selects the invention subject to examination on the basis of the first invention. [3]
Can a registered patent be invalidated for lack of unity?
No. Article 45 is not among the grounds for a trial for invalidation listed in Art. 133(1) of the Patent Act. [1] The Examination Guidelines also state that the unity requirement is not a ground for invalidation. [3]
Is there no unity problem if there is only one independent claim?
In principle, unity is not assessed between an independent claim and its dependent claims. [3] However, if the independent claim lacks novelty or inventive step over the prior art, a unity problem can arise among the claims that refer to that independent claim. [3]
The notice raised only lack of unity. Does that mean there are no other grounds for rejection?
No, that cannot be assumed. If the examiner finds it necessary for the efficient progress of examination, the examiner can first notify only the violation of Art. 45. In that case, the “Considerations of Amendment” section of the notice states that the requirements for patentability have not been examined for all the claims. [3]
Until when can a divisional application be filed for the invention of a deleted claim?
It can be filed in the period in which amendment is possible. It can also be filed within three months from service of the certified copy of the decision of rejection or of the decision to grant (Patent Act, Art. 52(1)). [1] The three months after a decision of rejection apply to applications for which the certified copy of the decision of rejection is served on or after 20 April 2022. [1] After a decision to grant, if the date when the applicant intends to have the grant of the patent registered is earlier, the period ends on that date. [1]
How DEFINE IP Law Firm handles this
DEFINE IP Law Firm checks unity at two stages. They are the stage of structuring the claims before filing and the stage of responding to a notice of grounds for rejection. Subject matter of claims that are removed is recorded separately as a candidate for a divisional application. For questions about claim structure and unity responses in Korean applications, please write to contact@defineip.kr.
Sources
- Patent Act (특허법), Act No. 21134, in force from 11 November 2025. Articles 45, 47, 52, 59, 62, 63, 63-2, 66-3, 67-2, 132-2 and 133; Addenda to Act No. 12753, Art. 8; Addenda to Act No. 13096, Art. 2; Addenda to Act No. 14035, Arts. 6, 10 and 21; Addenda to Act No. 18505, Arts. 3 and 7. https://www.law.go.kr/법령/특허법 (verified 9 October 2026)
- Enforcement Decree of the Patent Act (특허법 시행령), Presidential Decree No. 35809, in force from 1 October 2025. Article 6. https://www.law.go.kr/법령/특허법시행령 (verified 9 October 2026)
- Ministry of Intellectual Property (지식재산처), Patent Examination Guidelines (특허·실용신안 심사기준), MOIP Established Rule No. 7, in force from 13 March 2026. Part 2, Chapter 5 “Scope of Patent Application” (1특허출원의 범위); Part 5, Chapter 2, 3.2; Part 5, Chapter 3. https://www.law.go.kr/행정규칙/특허·실용신안심사기준 (verified 9 October 2026)
- Enforcement Rules of the Patent Act (특허법 시행규칙), Prime Ministerial Decree No. 2115, in force from 14 May 2026. Article 106-14. https://www.law.go.kr/법령/특허법시행규칙 (verified 9 October 2026)
- Patent Act (특허법), Act No. 21955, promulgated 15 September 2026, scheduled to take effect on 16 March 2027. Article 45. https://www.law.go.kr/법령/특허법 (verified 9 October 2026)
- WIPO, Regulations under the PCT, Rule 13 Unity of Invention, version in force from 1 January 2026. https://www.wipo.int/pct/en/texts/rules/r13.html (verified 9 October 2026)
- EPO, European Patent Convention, Article 82, Rule 44, Rule 64. https://www.epo.org/en/legal/epc/2020/r44.html , https://www.epo.org/en/legal/epc/2020/r64.html (verified 9 October 2026)
- US Code of Federal Regulations, 37 CFR 1.141, 1.142, 1.475, 1.499 (eCFR, shown as up to date as of 6 October 2026). https://www.ecfr.gov/current/title-37/section-1.142 (verified 9 October 2026)
- Patent Act (특허법), previous versions. Act No. 11848 (in force from 1 July 2014), Articles 45 and 133. Act No. 13096 (in force from 29 July 2015), Article 133. Version history at https://www.law.go.kr/법령/특허법 (verified 9 October 2026)