You are required to pay renewal fees to the European Patent Office EPO in respect of your European patent application so long as the patent grant has not been published. Annuities become due on the third and each subsequent year, calculated from the date of filing. Renewal fees are due on the last day of the month in which the anniversary of the date of filing falls. For example if you filed your patent on 15-Mar-18 the deadline to settle the annuity is on 31-Mar-21 each subsequent year. The last renewal fee payable to the EPO in respect of a European patent application covers the patent year in which the mention of the grant of the patent is published. After which you need to settle annuities at the different national patent offices of the designated states.