I have been told that a European patent application may be filed in any language. Since I am a Danish citizen, can I file my application in Danish? Do you need a translation? Will I have to file any other translations later on?

Yes, a European patent application may indeed be filed in any language. However, if the language is not one of the EPO’s official languages (English, French or German) you need to file a translation in one of the official languages within two months of filing the application. If the translation is not filed in due time, the EPO will invite you to correct this deficiency within two months. The official language into which the application is translated constitutes the language of the proceedings and cannot be changed at a later stage. If you fail to file the translation in due time in reply to the EPO’s invitation, the application will be deemed withdrawn. In such a case you may request re-establishment of rights under Article 122 EPC. 

If the examining division is of the opinion that the application and the invention to which it relates meet the requirements of the European Patent Convention, it will proceed to the grant of the European patent. At this point the applicant is invited to pay the fee for grant and publishing and to file translations of the claims in the two other official languages. 

Finally, after the grant of the European patent, a validation procedure - often including translation of the patent specification and/or claims - may have to be undertaken in order to validate the patent in the designated states. More information on the validation procedure and the language requirements of the contracting states can be found in the brochure “National Law relating to the EPC”. 

In addition, European patent proprietors can request unitary effect. If registered, the Unitary Patent currently covers the territory of the 17 EU Member States participating in this enhanced cooperation. More information on the procedure and requirements for obtaining unitary effect can be found on the EPO website (see links below).