IP Quick Tip: Which language to choose when drafting and filing a European patent application at the EPO

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The official languages at the EPO are English, French and German. However, it is possible to file a European patent application in any language, for example Italian or Swedish; and then to file a translation in one of the official languages. This is a common practice in my home country Spain: many applicants file a European patent application in Spanish and then file a translation in English.

However, it is important to bear in mind the risk involved in translating a patent application into another language. This is very difficult, as it is actually very hard for a translation to be 100% accurate and to convey exactly the same meaning as the original text. Often there are slight differences between the original application in Spanish and the translation in English.

The EPO has a well-deserved reputation for being very strict when it comes to added subject-matter and it is possible that even a slight translation error could cause a problem in terms of added subject-matter. A priority claim could actually even be deemed invalid by the EPO where the priority document is drafted in one language and the European application is drafted in another.

While it is possible to correct mistakes in translations and while the EPO does allow this, correcting mistakes can be problematic after grant when the possibilities to amend the claims are rather limited. So, while it can be very convenient to file European patent applications in a non-official language, applicants should proceed carefully and consider the whole patent life cycle when making such a decision.