PCT guide
PCT search report, written opinion and Chapter II
By Dharmik Patel, Co-founder, PatentAssist.ai
Updated
About 15 to 16 months after the priority date, a PCT application gets two documents from the International Searching Authority (ISA): the international search report, which lists prior art with a category code against each claim, and the written opinion, which says claim by claim whether the invention looks new, inventive and industrially applicable. This guide explains how to read both, what you can do about a negative opinion, and when a Chapter II demand is worth its fee.
Quick answer
- When: 3 months from the ISA's receipt of the search copy or 9 months from priority, whichever is later (Rule 42.1).
- Read: X and Y citations are the objections; Box No. V of the written opinion gives YES or NO per claim for novelty (N), inventive step (IS) and industrial applicability (IA).
- Amend the claims: Article 19, by 2 months from the search report or 16 months from priority, whichever is later. Not examined.
- Argue for free: informal comments to WIPO, ideally before 28 months. Not examined either.
- Get a new opinion: Chapter II demand by 3 months from the search report or 22 months from priority, whichever is later, with a handling fee (CHF 200) and the IPEA's examination fee.
What the ISA sends you, and when
The ISA must establish the international search report (ISR) within 3 months of receiving the search copy or 9 months from the priority date, whichever expires later ( Rule 42.1). At the same time it establishes the written opinion of the ISA ( Rule 43bis.1). Both come with a transmittal form, PCT/ISA/220, whose date of mailing starts the clocks for Article 19 amendments and the Chapter II demand.
The ISR ( Form PCT/ISA/210) is published with the application, and the written opinion ( Form PCT/ISA/237) is made public on PATENTSCOPE at the same time, together with any informal comments you file (ISPE Guidelines 2.17). If you landed here from a published PCT document, that is why you can read another applicant's opinion.
The overall PCT timeline, fees for filing and the national phase are covered in our PCT application guide . This page stays on the search report and what follows it.
Reading the search report: category codes
Each document in the ISR carries a category letter and the claims it relates to. The codes are defined in WIPO Standard ST.14 and in paragraphs 16.65 to 16.75 of the PCT Search and Examination Guidelines , and printed at the foot of the report. A document can carry different codes for different claims, for example X for claim 1 and Y for claims 2 to 5.
| Code | Meaning | How to read it |
|---|---|---|
| X | Particularly relevant on its own: the claimed invention cannot be considered novel, or cannot be considered inventive, when the document is taken alone. | The main threat. Box No. V will usually say NO for novelty or inventive step on the claims listed next to it. |
| Y | Particularly relevant in combination: the claimed invention cannot be considered inventive when the document is combined with one or more other Y documents, the combination being obvious to a person skilled in the art. | An inventive step objection built from two or more documents. Look for the other Y citations against the same claims. |
| A | Defines the general state of the art; not considered of particular relevance. | No objection by itself. |
| E | Earlier application or patent, filed or with a priority date before your international filing date but published on or after it (Rule 33.1(c)). May be combined with X, Y or A. | Not prior art in the international phase, but may be cited against novelty in national phases whose law counts earlier-filed applications. |
| P | Published before the international filing date but on or after the claimed priority date. Always paired with X, Y or A. | Only prior art if your priority claim fails for the claims concerned. Check that the priority document supports them. |
| O | Refers to an oral disclosure, use, exhibition or other means. Always paired with X, Y or A. | What counts is the date of the oral disclosure or use, not only the date of the document. |
| L | May throw doubt on a priority claim, or is cited to establish the publication date of another citation or for another stated reason. | Read the reason given. An L document aimed at your priority claim can turn a P document into prior art. |
| T | Later document, published after the international filing date or priority date and not in conflict with the application, cited to explain the principle or theory behind the invention. | Not prior art. Cited for understanding, or to show the reasoning or facts behind the invention are wrong. |
| D | Document you cited yourself in the application. Always paired with a relevance category, as in D,X. | The examiner is using your own background art against you. |
| & | Member of the same patent family as another cited document. | Usually a version in another language or country; the content is believed to be substantially the same. |
The EPO uses the same letters in its own search reports, with EPC-specific consequences; see our European search report guide if you have an extended European search report and search opinion rather than a PCT one. The ISR also has its own boxes for unsearchable claims (Box No. II) and lack of unity (Box No. III); a lack-of-unity finding means some claims may not have been searched at all.
Reading the written opinion: Box No. V and the other boxes
The heart of the written opinion is Box No. V, the reasoned statement on novelty, inventive step and industrial applicability. Item 1 is a grid:
Novelty (N) Claims 2-10 YES
Claims 1 NO
Inventive step (IS) Claims 6-10 YES
Claims 1-5 NO
Industrial applicability (IA) Claims 1-10 YES
Read it as: claim 1 is anticipated, claims 2 to 5 are new but obvious, and claims 6 to 10 are fine. The examiner must make the statement for each examined claim and back every NO with citations and reasons, which appear in item 2 of the box with passages of the cited documents (ISPE Guidelines 17.42 and 17.43; Rule 70.6). Claims 6 to 10 in this example are your fallback positions: the features they add are what the examiner could not find.
The other boxes of Form PCT/ISA/237:
- Box No. I, basis of the opinion: which language and documents were used.
- Box No. II, priority: whether the priority claim was found invalid, which can turn P documents into prior art.
- Box No. III: claims on which no opinion could be given, for example excluded subject matter or claims so unclear they could not be assessed.
- Box No. IV, lack of unity of invention.
- Box No. VI: certain documents cited, such as earlier-filed applications published later.
- Box No. VII: formal defects in the application.
- Box No. VIII: clarity and support objections. These are worth fixing early, because most offices will raise them again.
Article 19, informal comments or a Chapter II demand
After the search report you have three ways to react, and you can also do nothing. They differ in what you can change, who reads it and what it costs.
| Aspect | Article 19 | Informal comments | Chapter II demand |
|---|---|---|---|
| What you can change | Claims only, plus a statement of up to 500 words | Nothing; arguments only | Claims, description and drawings (Article 34), plus arguments |
| Filed with | International Bureau (Rule 46.2) | International Bureau | A competent IPEA, with the demand |
| Deadline | 2 months from transmittal of the ISR or 16 months from priority, whichever is later (Rule 46.1) | No rule; WIPO recommends before 28 months so offices get them at 30 | Demand: 3 months from transmittal of the ISR and opinion or 22 months from priority, whichever is later (Rule 54bis.1) |
| Official fees | None in the PCT Schedule of Fees | None in the PCT Schedule of Fees | Handling fee plus the IPEA's preliminary examination fee |
| Does an examiner look at it? | No | No | Yes, the IPEA examines it |
| What the offices receive at 30 months | The IPRP (Chapter I), which still repeats the original opinion; the amended claims are published with the application | The IPRP (Chapter I) together with your comments | A new IPRP (Chapter II) on the amended application |
Example: priority date 13 March 2025, PCT filed 13 March 2026, search report and opinion mailed 15 July 2026. The Article 19 deadline is 15 September 2026 (2 months from mailing, later than the 16-month date of 13 July 2026). The demand deadline is 13 January 2027 (22 months from priority, later than 3 months from mailing). A deadline that falls on a day the office is closed moves to the next working day (Rule 80.5).
Article 19 amendments
Article 19 gives one chance to amend the claims, and only the claims, before the International Bureau. File a complete replacement claim set with a letter that identifies the changes and their basis in the application as filed ( Rule 46.5). You may add a statement explaining the amendments, of no more than 500 words, which must not disparage the search report (Rule 46.4). Amendments arriving after the deadline are still accepted if they reach WIPO before the technical preparations for publication are complete (Rule 46.1).
Nobody examines them in Chapter I, and the IPRP (Chapter I) does not take them into account (ISPE Guidelines 2.18). Their value is that the amended claims are published, which matters in countries that give provisional protection from publication (Applicant's Guide 9.011). If you file a demand, Article 19 amendments made before it are taken into account by the IPEA unless you replace them under Article 34.
Informal comments on the written opinion
The PCT Regulations have no formal procedure to answer the written opinion in Chapter I. By decision of the PCT Assembly, you can send informal comments to the International Bureau instead (Applicant's Guide 7.030). There is no word limit, and WIPO accepts them in any language. WIPO recommends filing them before 28 months from priority; comments received after 30 months stay in WIPO's file and are not sent to the designated offices. If you later file a demand, the comments are not forwarded either, though they stay public on PATENTSCOPE.
They are not examined, and the IPRP (Chapter I) still repeats the original opinion. Their use is to put your rebuttal in front of every national examiner who reads that report, at no fee.
The IPRP (Chapter I)
If no demand is filed, the International Bureau issues the international preliminary report on patentability (Chapter I) on behalf of the ISA. It has the same content as the written opinion and is sent to the designated offices, not before 30 months from the priority date ( Rule 44bis). So "IPRP versus written opinion" is mostly a question of title and timing: same text, different cover sheet.
Chapter II: the demand for international preliminary examination
A demand asks an International Preliminary Examining Authority (IPEA) for a second, examined opinion. It is filed on Form PCT/IPEA/401 ( Rule 53) directly with an IPEA that is competent for your application; which ones are competent depends on the receiving Office, the language and the ISA (Applicant's Guide 10.006 and Annexes C and E). The deadline is 3 months from transmittal of the ISR and written opinion or 22 months from priority, whichever is later ( Rule 54bis.1). A late demand is treated as not submitted.
Article 34 amendments and the reply
Under Article 34(2)(b) you can amend the claims, description and drawings, within the original disclosure, until the report is drawn up. In practice the ISA's written opinion is usually treated as the IPEA's first written opinion ( Rule 66.1bis), and the form invites your reply with amendments before the demand deadline. So file the amendments and arguments with the demand. If the IPEA issues a further written opinion, the reply period is usually 2 months (Applicant's Guide 10.066). The IPEA's time limit for the report is 28 months from priority, or 6 months from the start of examination if that is later ( Rule 69.2), so there is rarely time for more than one round. You are not obliged to amend; you can accept a negative report and argue in the national phase instead (Applicant's Guide 10.069).
Fees
Every demand pays a handling fee for WIPO, CHF 200 in the Schedule of Fees (Rule 57), reduced by 90% for some applicants from qualifying countries, and a preliminary examination fee that each IPEA sets for itself ( Rule 58). Both are due 1 month from filing the demand or 22 months from priority, whichever is later. Examples from WIPO's PCT Fee Tables, Table II, amounts on 1 October 2026:
| IPEA | Preliminary examination fee | Handling fee |
|---|---|---|
| European Patent Office | €2,010; a 75% reduction applies under certain conditions (Applicant's Guide Annex E) | €215 |
| USPTO | $705 if the USPTO was the ISA, $880 otherwise; small entity $282 / $352, micro entity $141 / $176 | $251 |
| Indian Patent Office | ₹10,000 if it was the ISA, ₹12,000 otherwise; ₹2,500 / ₹3,000 for natural persons, startups, small entities and educational institutions | $251 |
The IPRP (Chapter II)
The result is the international preliminary report on patentability (Chapter II), with the same YES/NO statement as Box No. V, now based on your amended application (Rule 70.6). It replaces the Chapter I report and goes to the elected offices with your amendments annexed. It is not binding on them, but WIPO notes it carries considerable weight, and an office that was itself the IPEA will generally proceed quickly to grant on a favourable report (Applicant's Guide 10.083).
Is Chapter II worth it?
A demand no longer buys time for national phase entry, except at two offices and only if filed before 19 months from priority; see PCT national phase deadlines . So the question is only whether a better report is worth the fees and the work. Some practical signals:
- Often worth it when the opinion is negative but you have a clear amendment or a strong argument, and you will enter several offices that give weight to the report, or the office you care most about is the IPEA itself.
- Often not worth it when the opinion is already positive, when you will enter only one or two offices and can amend there, or when you still need to decide on claim scope per country.
- Middle ground: informal comments, at no fee, if you mainly want your side on the record.
This is a strategy decision with cost and scope consequences in every country. Discuss it with your patent attorney or agent before the demand deadline.
What national offices do with these reports
Each designated or elected office examines under its own law and is not bound by the IPRP. The European Patent Office is the clearest example of an office acting directly on the PCT opinion. Where the EPO was the ISA (and the IPEA, if a demand was filed), it invites you after European phase entry to comment on its written opinion or IPRP and correct the deficiencies within 6 months; if you do not answer such an invitation, the application is deemed withdrawn ( Rule 161(1) EPC; see our Rule 161 EPC page). A negative PCT opinion from the EPO therefore becomes a reply you must file in Europe. Where another office was the ISA, the EPO usually draws up a supplementary European search instead; see the Euro-PCT regional phase guide . For the United States, see our guide to the US national stage .
Check the cited documents yourself
Before you amend or argue, read the X and Y documents in full and look for anything closer that the ISA missed. PatentAssist.ai searches EPO, USPTO and Indian patent records in one place, so you can pull up the citations and their family members and test your fallback claims against them. It does not file amendments or demands for you.
More patent guides
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PCT search report and written opinion: frequently asked questions
What is the written opinion of the International Searching Authority?
It is the examiner's preliminary view, issued with the international search report, on whether each claim appears novel, inventive and industrially applicable, and on certain formal defects (PCT Rule 43bis.1). It is made public on PATENTSCOPE when the application is published. If you do not file a Chapter II demand, the International Bureau reissues it unchanged as the international preliminary report on patentability (Chapter I).
What do X, Y and A mean in an international search report?
X means a document that on its own shows a claim is not new or not inventive. Y means a document that shows lack of inventive step when combined with one or more other Y documents. A means general background that is not particularly relevant. Other codes are E (earlier-filed patent document published on or after your filing date), P (published between priority and filing date), O (oral disclosure), L (cited for another reason, often priority), T (later theory document), D (cited in your own application) and & (same patent family).
What does 'Novelty (N) Claims ... YES' mean in Box No. V?
Box No. V of the written opinion lists, for each criterion, the claims that meet it (YES) and the claims that do not (NO). N is novelty, IS is inventive step and IA is industrial applicability. 'Novelty (N) Claims 1-10 YES' together with 'Inventive step (IS) Claims 1-5 NO' means the examiner found claims 1 to 10 new, but claims 1 to 5 obvious. Item 2 of the box gives the documents and reasons.
Can I respond to the written opinion, and what is the deadline?
There is no formal response in Chapter I. You can send informal comments to the International Bureau; WIPO recommends filing them before 28 months from priority so they go to the designated offices with the report at 30 months. A formal reply, examined by an examiner, is only possible under Chapter II: file a demand, with Article 34 amendments and arguments, by 3 months from transmittal of the search report and opinion or 22 months from priority, whichever is later.
What is the difference between the IPRP and the written opinion?
The IPRP (Chapter I) has the same content as the written opinion of the ISA; the International Bureau simply reissues it under that title and sends it to the designated offices, not before 30 months from priority (Rule 44bis). It does not take Article 19 amendments into account. The IPRP (Chapter II) is different: it is a new report by the IPEA after examining your demand, amendments and arguments.
What is the Chapter II demand deadline?
3 months from the date the search report and written opinion were transmitted to you, or 22 months from the priority date, whichever expires later (PCT Rule 54bis.1). A demand filed after that is treated as not submitted. For most applications the 22-month date is the later one.
How much does a Chapter II demand cost?
Two fees: the handling fee (CHF 200 in the PCT Schedule of Fees, collected in the IPEA's currency, for example €215 at the EPO or $251 at the USPTO) and the preliminary examination fee set by each IPEA. On WIPO's fee table of 1 October 2026 that is €2,010 at the EPO, and $705 at the USPTO when it was also the ISA ($880 otherwise, less for small and micro entities). Both are due 1 month from filing the demand or 22 months from priority, whichever is later.
Should I file Article 19 amendments if I am filing a demand?
Usually not. WIPO's Applicant's Guide says there is normally no need to amend under Article 19 when a demand is filed, because Article 34 lets you amend the claims, description and drawings before the IPEA anyway. The exception is when you want narrower claims published with the application, for example for provisional protection in countries that offer it.
Sources: PCT Article 19 and 34 ; PCT Rules 33.1 , 42.1 , 43bis.1 , 44bis , 46 , 53 , 54bis.1 , 57 , 58 , 66.1bis , 69.2 and 70.6 and the Schedule of Fees ; Forms PCT/ISA/210 and PCT/ISA/237 ; PCT International Search and Preliminary Examination Guidelines (in force 1 January 2026); WIPO Standard ST.14 ; WIPO PCT Applicant's Guide , International Phase; WIPO PCT Fee Tables (amounts on 1 October 2026); Rule 161 EPC . Checked 2 November 2026. This guide is general information, not legal advice. Confirm deadlines and fees with a patent attorney or agent before you act.