A patent can still be declared invalid after the opposition period has expired.
When the opposition period has expired, your patent can still be declared invalid if someone initiates proceedings before the Patent and Market Court (Patent- och marknadsdomstolen) a division of the District Court of Stockholm. Where a European patent is concerned, however, annulment issues are normally resolved before the Unified Patent Court (UPC).
In principle, an appeal for annulment of a national Swedish patent can be made on the same grounds as an opposition. Anyone who wants to initiate court proceedings must notify us at PRV as well as inform everyone who has a licence or pledge for the patent.