UEFA has organised several ticket return phases: the first one in May 2020, the second one in June 2020, the third one in January 2021 and the last one in March-April 2021.
The Ticket Return Portal is closed and there will be no further ticket return phase for UEFA EURO 2020.
However, in situations where:
a reduction of stadium capacity may occur
a match may be played behind closed doors
a match may be cancelled