This section is intended to summarise all formal requirements relating to priority claims in international applications. In the present edition, it focuses on formal requirements under Rule 4.10, defects in priority claims and corrections upon invitation as well as restoration of the priority right. It also provides additional information on the applicant's entitlement to claim priority under Article 87 EPC in the European phase before the EPO. Further relevant aspects will gradually be added in successive editions. For further information see GL/PCT‑EPO F‑VI.