An applicant wishing to claim priority must file a declaration of priority indicating the date of the previous application, the State in or for which it was filed and its file number. The date and State of the previous application must be stated in the request for grant at the time of filing the European patent application. The request for grant may be corrected under Rule 88, first sentence, if it contains errors regarding the date and State of the earlier application, provided that the request for correction is made sufficiently early for the correction to be contained in the publication of the application or at least for a warning to be included in the published application. If the request is filed later it may, exceptionnaly, be allowed if it is apparent on the face of the published application that a mistake has been made (see V, 3 and other sources therein). The file number of the previous application must be indicated before the end of the sixteenth month after the date of priority claimed; failure to do so constitutes a deficiency which the applicant is requested to rectify (under application mutatis mutandis of the principles of J 1/80, OJ 9/1980, 289).