According to Article 75 of the European Patent Convention (EPC)
(1)
A European patent application may be filed:
(a)
with the European Patent Office, or
(b)
if the law of a Contracting State so permits, and subject to Article 76, paragraph 1, with the central industrial property office or other competent authority of that State. Any application filed in this way shall have the same effect as if it had been filed on the same date with the European Patent Office.