The copy of the priority application which is required for the request according to Rule 56(3) does not need to be certified. However, if the applicants do provide a certified copy in the context of their request according to Rule 56(3), they will not need to provide it again in the context of their priority claim according to Rule 53(1).
Where a copy of the priority document is already available to the EPO under Rule 53(2) in accordance with the conditions laid down by the President, the applicant does not need to file it. See also A‑III, 6.7.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/a_ii_5_4_3.htm
Date retrieved: 17 May 2021