You can initiate cancellation proceedings for an EU mark by filing a cancellation application with the EUIPO's Cancellation Division. These are submitted online through the EUIPO portal.
The cancellation application must identify the trademark to be cancelled, state the grounds (non-use, or that the mark has become generic or deceptive), and include payment of the cancellation fee. The trademark owner is then notified and given the opportunity to respond.
Non-use cancellations require the applicant to show that the trademark has not been put to genuine use in the EU for a continuous five-year period. The burden then shifts to the trademark owner to provide evidence of genuine use.