There is no obligation to file a confirmation copy of subsequent documents, but the receiving Office may require one to be submitted (see point 69
) and will do so in particular if the applicant has submitted substitute sheets under Rule 26 PCT
and/or any sheets to be incorporated by reference under Rule 20.6 PCT
. In these two cases the applicant is advised to submit a confirmation copy on his own initiative directly after sending the sheets concerned by fax.