What arrives during the international phase
After an international application is filed, the International Searching Authority searches the prior art and produces two documents at the same time. One is a list of the documents it found — the international search report. The other is an opinion on whether the invention appears patentable in light of those documents — the written opinion. They are separate documents and they do different work.
| Document | Basis | When | Binding? |
|---|---|---|---|
| International search report (ISR) | Article 18 · Rule 42.1 | Three months from receipt of the search copy, or nine months from the priority date, whichever expires later | No |
| Written opinion of the ISA (WO-ISA) | Rule 43bis.1 | Established together with the ISR | No |
| International preliminary report on patentability, Chapter I | Rule 44bis | Issued by the International Bureau with the same content as the written opinion, where no Chapter II demand is made | No · not communicated to designated Offices before 30 months from the priority date |
The search report is a list, not a verdict
Article 18 provides that the international search report is established within the prescribed time limit and in the prescribed form, and transmitted to the applicant and the International Bureau as soon as it has been established. The report itself lists the documents considered relevant to the invention. The assessment of patentability is made not here but in the next document, the written opinion.
- Time limit
- 3 months from the search copy / 9 months from priority, later of the two Rule 42.1
- Transmitted to
- The applicant and the International Bureau Article 18(2)
- Nature
- A list of prior art — not a patentability decision
The written opinion — preliminary and non-binding
Rule 43bis.1 requires the International Searching Authority to establish a written opinion at the same time as the search report. It covers two things: whether the claimed invention appears to be novel, to involve an inventive step and to be industrially applicable; and whether the international application complies with the requirements of the Treaty and the Regulations. The criteria of Article 33(2) to (6) apply mutatis mutandis.
Where no demand for international preliminary examination is filed, the International Bureau issues a report with the same substance as the written opinion, titled the international preliminary report on patentability (Chapter I) (Rule 44bis.1). That report is not communicated to designated Offices before the expiration of 30 months from the priority date (Rule 44bis.2(a)).
Article 19 — claims only, one opportunity, filed with the IB
Article 19(1) reads: the applicant shall, after having received the international search report, be entitled to one opportunity to amend the claims of the international application by filing amendments with the International Bureau within the prescribed time limit. Four things follow from that sentence — the subject is the claims, the count is one, the place is the International Bureau, and 'entitled to' is the language of a right.
- What may be amended
- The claims only Not the description or the drawings
- How many times
- One opportunity Article 19(1)
- Where filed
- Directly with the International Bureau Rule 46.2
- Time limit
- 2 months from transmittal of the ISR / 16 months from priority, later of the two Rule 46.1
- Limit
- Must not go beyond the disclosure of the application as filed Article 19(2)
Amendments received after the time limit are nevertheless considered timely if they reach the International Bureau before the technical preparations for international publication have been completed (Rule 46.1). That is a saving provision, not slack you can plan around — the date on which technical preparations complete is not under the applicant's control.
- File replacement sheets containing a complete set of claims as amended — not just the changed parts.
- Identify which claims have been amended.
- Show how the amended claims differ from the claims as originally filed.
- State which claims, if any, have been cancelled.
- Indicate the basis for the amendments in the application as filed, in the accompanying letter (Rule 46.5).
A statement may accompany the amendments (Rule 46.4). It explains the amendments and their relationship to the documents cited in the search report, must not exceed 500 words in English, and must not contain disparaging comments on the search report or on the relevance of the citations — except in the context of explaining an amendment to a particular claim.
Is it mandatory? No.
| Reasons to amend now | Reasons to wait |
|---|---|
| You want the amended claims to appear in the international publication | You have not yet heard from local counsel in the target countries |
| The citations are clear and you have already decided how to narrow the claims | You plan to pursue different claim sets in different countries |
| You expect many national phases and do not want to repeat the same amendment in each | The description or drawings also need to change — Article 19 cannot reach them |
| The objection is met by a change of claim wording alone | You want to argue against the objection rather than narrow the claims |
If you want to argue back — three routes
An Article 19 amendment changes the claims; it is not a procedure for replying to the written opinion. If you want to contest the reasoning itself, there are three routes, and they are not interchangeable.
| Route | Filed with | Time limit | Publicly available? |
|---|---|---|---|
| Statement under Article 19 | International Bureau | Same time limit as the Article 19 amendment | Published with the international application · 500 words in English |
| Informal comments | International Bureau | No prescribed time limit · recommended before 28 months from priority | Made available on PATENTSCOPE · no length limit |
| Demand for Chapter II examination with Article 34 amendments | International Preliminary Examining Authority | 3 months from transmittal of the ISR and written opinion / 22 months from priority, later of the two | Report communicated to designated Offices after 30 months |
Under Chapter II the applicant may amend the claims, the description and the drawings (Article 34(2)(b)) and may respond to the written opinion of the Examining Authority (Article 34(2)(d)). The same limit applies — no amendment may go beyond the disclosure as filed. The Authority must also issue at least one written opinion before establishing its report, subject to the conditions in Article 34(2)(c).
Korea — an international amendment does not carry over by itself
- Patent Act Article 201(1) — for an international application filed in a foreign language, the Korean translation must be submitted within 2 years and 7 months (31 months) from the priority date.
- Patent Act Article 201(2) — where an Article 19 amendment was made, the translation of the claims as amended may be submitted in place of the translation of the claims as originally filed.
- Patent Act Article 204(1) — by the reference date, submit the Korean translation of the amendment (foreign-language filing) or a copy of it (Korean-language filing).
- Patent Act Article 204(3) — a statement under Article 19 filed with the International Bureau is submitted in the same way.
- Patent Act Article 205 — amendments under Article 34 are governed by a separate provision.
In short, an amendment survives in Korea only if both steps exist: the act in the international phase and the document filed domestically. This is where portfolio management usually slips — the fact that an amendment was filed with the International Bureau is recorded, and the domestic translation deadline passes unnoticed.
Dates you cannot undo
| Point in time | What | Basis |
|---|---|---|
| 2 months from transmittal of the ISR, or 16 months from priority, whichever is later | Article 19 amendment | Rule 46.1 |
| 18 months from priority | International publication | Article 21(2)(a) |
| 22 months from priority | Request for supplementary international search | Rule 45bis.1(a) |
| 3 months from transmittal of the ISR and written opinion, or 22 months from priority, whichever is later | Demand for international preliminary examination | Rule 54bis.1(a) |
| 28 months from priority | Recommended deadline for informal comments | PCT Applicant's Guide |
| 30 months from priority | Entry into the national phase | Article 22(1) · Article 39(1)(a) |
| 2 years and 7 months from priority | Korean domestic document submission period | Korean Patent Act Article 201(1) |
Sources
- PCT Articles 18, 19, 21, 22, 33, 34 and 39.
- PCT Rules 42.1, 43bis.1, 44bis, 45bis.1, 46.1, 46.2, 46.4, 46.5 and 54bis.1.
- PCT Applicant's Guide, International Phase, paragraph 7.030, and PCT Newsletter 01/2015 Practical Advice — informal comments on the written opinion.
- Korean Patent Act Articles 201, 204 and 205.
This article reflects the texts of the Treaty, the Regulations and the Korean Patent Act as verified in August 2026. The Treaty and Regulations are amended over time and national time limits change independently, so for any live case the current texts and the country-specific information for the intended Offices should be checked.