A translation of the previous application into one of the official languages of the EPO is required only if it is needed for determining the validity of the priority claim, where this is of relevance to the patentability of the underlying invention. The translation must be filed within the time limit set by the EPO. For more details on the procedure see A‑III, 6.8 and sub-sections.
Alternatively, under Rule 53(3), a declaration that the European patent application is a complete translation of the previous application may be submitted within that same time limit. This declaration must be unambiguous, stating that the translation is "complete" or, for example, "identical" or "literal". Declarations in diluted or modified form (stating, for example, that the translation is "practically complete" or that the contents "are essentially the same") cannot be accepted. The same applies to cases where the declaration is obviously incorrect (e.g. if several priorities are claimed for a single European application or if the European application contains more or less text than is contained in the previous application as filed). In all these cases a complete translation must be filed. Where the European application contains claims on its date of filing and the priority application did not contain claims on its filing date or contained fewer claims on its filing date than the subsequent European application, the declaration cannot be accepted. A merely different arrangement of the various elements of the application (e.g. presenting the claims before the description, or vice versa) does not affect the validity of such a declaration. See also A‑III, 6.8.6.
If the applicant has already provided the EPO with a translation of the priority document as part of a request under Rule 56 (see A‑II, 5.4(vi)) to base missing parts of the description or drawings on the priority application itself, then there is no need for the applicant to file the translation a second time.
The request for translation cannot be made by telephone (regardless of whether this is mentioned in the minutes). Because of the time limit and its possible legal consequences, the request must always be made in writing. In examination proceedings it may be issued alone or may accompany a communication under Art. 94(3). The translation of the priority document may become necessary only at later stages of the examination procedure, when documents are retrieved by carrying out a "topping-up" search for conflicting applications under Art. 54(3) (see C‑IV, 7.1, and A‑III, 6.8.2). This may also happen during opposition proceedings where the applicant was not requested to file the translation before grant and the opponent raises patentability issues which require examination of the validity of the priority.
If the required translation or declaration is not filed within the time limit, the right of priority is lost and the applicant or proprietor is informed accordingly (see A‑III, 6.11). This has the effect that the intermediate document(s) will become prior art under Art. 54(2) or Art. 54(3), as applicable, and therefore relevant for the assessment of patentability (see A‑III, 6.8.3). However, for reasons of legal certainty the right of priority remains effective for determining the state of the art for the purposes of Art. 54(3) (see F‑VI, 2.1 and F-VI, 3.5) in respect of any other European patent application. In that respect it is immaterial whether the translation or declaration has been filed, as changes taking effect after the date of publication do not affect the application of Art. 54(3).
If the required translation or declaration is filed within the time limit, ideally with accompanying observations, the extent of the validity of the priority and the co-dependent substantive issues will be examined.