An applicant may address a notice of withdrawal of one or more priority claims to the IB, the RO or, where a demand has been filed, to the IPEA, and may do so at any time prior to the expiration of 30 months from the priority date.
Where the priority date of the international application has changed following withdrawal of a priority claim, any time limit which is computed from the original priority date, and which has not already expired, is recomputed from the priority date resulting from that change. Time limits computed from the original priority date which have already expired are not reinstated (Rule 90bis.3(d)). Nevertheless the IB may proceed with the international publication based on the original priority date if the notice of withdrawal of a priority claim reaches the IB after completion of the technical preparations for publication (Rule 90bis.3(e)).
The EPO acting as RO or as IPEA will mark the notice of withdrawal with the date on which it was received and promptly transmit it to the IB.
PCT AI section 326