Euro 2020 teams hit by Covid outbreaks this summer will have to fulfil fixtures even if they have as few as 13 players available, including a goalkeeper.
The Premier League introduced a similar rule at the start of this season, requiring clubs to fulfil fixtures if they had 14 available players, but later opted to postpone a number of fixtures following coronavirus outbreaks, prompting some managers to question whether it was being enforced.
Uefa has already confirmed that nations can name increased squads of 26 players, up from 23, as a result of the pressures of the pandemic on players.
If a nation is not able to name a squad of 12 outfield players and a goalkeeper, the match may be rescheduled within the next 48 hours and could also be moved to a different venue in another country, if necessary.
If a rescheduling is impossible, the nation with the outbreak will be forced to forfeit the match in a 3-0 defeat.
Uefa has also ruled that referees could take charge of their own nations at the tournament if the designated official is unavailable due to Covid.
Referees are usually prohibited from officiating internationals involving their home countries due to accusations of bias but Uefa could make an exception for the tournament and also use referees who are not approved by FIFA.