Linguistic errors, errors of transcription and mistakes in any document filed with the EPO may be corrected on request. Requests for such amendments may be made at any time, provided that proceedings are pending before the EPO (see J 42/92). However, if the error to be corrected concerns items which third parties might expect to be able to take at face value, so that their rights would be jeopardised by correction, the request for correction must be filed as soon as possible, and at least in time that it could be incorporated in the publication of the European patent application. With regard to correction of priority claims, specific provisions apply, with a view to protecting the interests of third parties, which allow the applicant to correct priority claims and lay down a time limit for doing so (see Rule 52(3) and A‑III, 6.5.2). This ensures that corrected priority information is available when the application is published. The applicant can only correct the priority claim later than this date, in particular after publication of the application, under certain limited circumstances, where it is apparent on the face of the published application that a mistake has been made. See J 2/92, J 3/91 and J 6/91 as well as J 11/92 and J 7/94. Each of these decisions indicated situations under EPC 1973 in which the correction of priority data too late for a warning to be published with the application could be allowed. These same situations apply mutatis mutandis under EPC 2000 to the acceptance of requests to correct priority claims after the end of the time limit according to Rule 52(3). Regarding correction of the date indicated for the previous filing, see also A‑III, 6.6.
If the error is in the description, claims or drawings, the correction must be obvious in the sense that it is immediately evident that nothing else could have been intended than what is offered as the correction. Such a correction may be effected only within the limits of what a skilled person would derive directly and unambiguously, using common general knowledge, and seen objectively and relative to the date of filing, from the whole of the documents as filed (see G 3/89 and G 11/91; see also H‑VI, 2.2.1). The documents to be considered in assessing whether or not the correction is allowable are those of the application as originally filed, including any late-filed missing parts of the description, or drawings filed according to Rule 56, regardless of whether this resulted in a change of the date of filing (see A‑II, 5 et seq). However, claims filed after the filing date in response to an invitation according to Rule 58 (see A‑III, 15) cannot be used in assessing the allowability of the request.
It is in particular not allowable to replace the complete application documents (i.e. description, claims and drawings) by other documents which the applicant had intended to file with his the request for grant (see G 2/95). The examining division decides on the request for correction. If a request for correction is pending before termination of the technical preparations for publication, a reference to the request is published on the front page.
In the case of electronic filing of European patent applications, the technical documents (description, claims, abstract and drawings) may be attached in their original format, provided this format is one listed in the Decision of the President of the EPO dated 12 July 2007, Special edition No. 3, OJ EPO 2007, A.5. Pursuant to this decision, these technical documents may also be attached in a format other than those listed, provided that the applicant informs the EPO, when filing the application, where the EPO can reasonably acquire the corresponding software. If, on the date of filing, the documents making up the European patent application are available both in the format provided by the EPO Online Filing software and in another admissible format in accordance with the above-mentioned Notice, the documents in the latter format can also be used in order to determine whether a request for correction of the description, claims, or drawings is allowable.