Rule 18

1. [Request]
a) Where an application, a patent or any request communicated to the Office in respect of an application or a patent contains a mistake, not related to search or substantive examination, which is correctable by the Office under the applicable law, the Office shall accept that a request for correction of that mistake in the records and publications of the Office be made in a communication to the Office signed by the applicant or owner and containing the following indications:
(i) an indication to the effect that a correction of mistake is requested;
(ii) the number of the application or patent concerned;
(iii) the mistake to be corrected;
(iv) the correction to be made;
(v) the name and address of the requesting party.
b) A Contracting Party may require that the request be accompanied by a replacement part or part incorporating the correction or, where paragraph 3 applies, by such a replacement part or part incorporating the correction for each application and patent to which the request relates.
c) A Contracting Party may require that the request be subject to a declaration by the requesting party stating that the mistake was made in good faith.
d) A Contracting Party may require that the request be subject to a declaration by the requesting party stating that the said request was made without undue delay or, at the option of the Contracting Party, that it was made without intentional delay, following the discovery of the mistake.

2. [Fees]
a) Subject to subparagraph b), a Contracting Party may require that a fee be paid in respect of a request under paragraph 1.
b) The Office shall correct its own mistakes, ex officio or upon request, for no fee.

3. [Single Request] Rule 16(5) shall apply, mutatis mutandis, to requests for correction of a mistake, provided that the mistake and the requested correction are the same for all applications and patents concerned.

4. [Evidence] A Contracting Party may only require that evidence in support of the request be filed with the Office where the Office may reasonably doubt that the alleged mistake is in fact a mistake, or where it may reasonably doubt the veracity of any matter contained in, or of any document filed in connection with, the request for correction of a mistake.

5. [Prohibition of Other Requirements] No Contracting Party may require that formal requirements other than those referred to in paragraphs 1 to 4 be complied with in respect of the request referred to in paragraph 1, except where otherwise provided for by the Treaty or prescribed in these Regulations.

6. [Notification; Non-Compliance with Requirements] Rule 15(6) and (7) shall apply, mutatis mutandis, where one or more of the requirements applied under paragraphs 1 to 3 are not complied with, or where evidence is required under paragraph 4.

7. [Exclusions]
a) A Contracting Party may exclude the application of this Rule in respect of changes in inventorship. What constitutes inventorship shall be determined under the applicable law.
b) A Contracting Party may exclude the application of this Rule in respect of any mistake which must be corrected in that Contracting Party under a procedure for reissue of the patent.