Despite the fact that R. 88, first sentence, EPC 1973 allowed correction without any time bar, the Legal Board followed the established case law requiring a request for correction of a priority claim to be made sufficiently early for a warning to be included in the publication of the application (J 3/82, OJ 1983, 171; J 4/82, OJ 1982, 385; J 14/82, OJ 1983, 121). This principle was upheld because the EPO, when exercising its discretionary power under R. 88, first sentence, EPC 1973 had to balance the applicant's interest in gaining optimum protection and a third party's interest in maintaining legal security and, in particular, in ensuring that the published application data were correct.
The board in J 6/91 noticed, however, that the previous case law in special circumstances already allowed the correction even without such a warning:
(i) if the EPO was partly responsible for the fact that no warning was published (J 12/80, OJ 1981, 143) and/or
(ii) if the interest of the public was not seriously affected because
- the mistake was obvious (in this sense, implicitly, J 8/80, OJ 1989, 293);
- the public was otherwise informed about the full scope of protection sought by the applicant (J 14/82, OJ 1983, 121).
In J 3/91, J 6/91 and J 2/92 it was held that even after publication of a European patent application without a warning, the priority declaration could be corrected under R. 88, first sentence, EPC 1973 provided that there was an obvious discrepancy in the published application indicating that something was wrong. In such a case the interests of third parties were not adversely affected by the correction.
In J 3/91 the board held that an experienced practitioner could have noticed the obvious discrepancy because the claimed Japanese priority date (31.12.1983) and the European application date (3.1.1984) were close together and the Japanese file number was mentioned.
In J 6/91 the international application in suit claiming priority from a US continuation-in-part application was itself presented as a continuation-in-part application and referred back to an earlier US application. In view of this and other special circumstances, the board allowed the addition of a (first) priority claim referring to the earlier US application.
In J 2/92 the US priority date claimed for a PCT application was, owing to a clerical error, a Saturday when the USPTO was closed, instead of the previous Friday. The correct date was indicated on the priority document. Owing to a further clerical error in the request for transmittal of priority documents under R. 17.1(b) PCT (a typing error in the document number), the Receiving Office - in this case the USPTO - transmitted the wrong document to WIPO. The board allowed its replacement even after publication of the international application, adding, however, that this might not always be possible (see also T 33/06).
In the parallel cases T 972/93 and T 973/93 the examining division had refused a request for the priority date to be corrected. European patent application E1 claimed the priority of a French application F1, from which two French divisional applications F2 and F3 were filed within the priority year claiming the priority of the parent application. At issue in T 972/93 and T 973/93 were European applications E2 and E3, which claimed the priority of F2 and F3 respectively. In error however, the filing date of F2 and F3 was given as the priority date. This mistake was detected during examination proceedings, after E2 and E3 had been published with the wrong priority date, because E1 was discovered as a prior right within the meaning of Art. 54(3) EPC 1973 (Art. 54 EPC has been substantially amended - see Chapter I.C. "Novelty").
The board of appeal allowed the correction (following J 6/91, OJ 1994, 349), ruling that the mistake was apparent, because only eight months separated the filing date of E2 and E3 from the incorrect priority date, whereas the priority year was usually exploited to the full. The interests of third parties had not been adversely affected because the precautionary filing of two European divisional applications with respect to E1, which had the same content as F2 and F3, made it possible to gain protection for the subject-matters of E2 and E3 with the priority of F1.
On the other hand, in J 7/94 (OJ 1995, 817) the board did not allow the correction. It held that the mere fact that an existing priority was not claimed could not justify adding this priority by correction. The correction of priority data, not requested sufficiently early for a warning to be included in the publication of the application, was only allowable if it was justified by special circumstances (confirming J 6/91, OJ 1994, 349). See also T 796/94.
In J 11/92 (OJ 1995, 25) it was held that an incomplete priority declaration could be corrected, by the addition of an omitted priority in special circumstances, even after publication of the European patent application without a warning to the public that a request for correction had been made, provided that the public had been informed about the full scope of European patent protection sought, by way of a second European or Euro-PCT patent application, filed as a precautionary measure by the applicant in due time (referring to J 6/91, OJ 1994, 349).
In T 713/02 (OJ 2006, 267), the board held that the examination of a request for correction of priority data after the publication of the application was not to be restricted to that portion of the facts and circumstances which in a decision of a board of appeal in another case were considered not to preclude the correction. Therefore, in the case before the board, it could not be ignored that the requested correction by addition of an earlier priority date would eliminate from the state of the art pursuant to Art. 54(2) EPC 1973 a highly relevant document, which the applicant had previously de facto accepted as comprised in that state of the art (see, however, the Notice from the European Patent Office regarding decision T 713/02 (OJ 2006, 293), according to which the EPO's departments of first instance do not, for the time being, follow the findings that no decisions, except where a total loss of rights should be remedied, may be taken in the applicant's favour prior to the decisions terminating the granting procedure).