The four-division format means that one of Europe’s 16 lowest-ranked teams is guaranteed to qualify for the Euros.
UEFA first approved the tournament in 2014, and has decided to split the 55 countries into four so-called ‘leagues’, based on its coefficient rankings.
The event changes European Championship qualifying, with one team from each Nations League division to reach Euro 2020, with the other 20 places going to the top two sides from the 10 groups of the subsequent, traditional qualifiers.
The top division is 12 teams strong and will be split into four groups of three, with the winners playing the Nations League finals in June 2019 to decide an overall winner.
The top-four ranked teams from each Nations league that fail to qualify for the Euros in the traditional route will enter play-offs in March 2020 to decide the last four places for the first finals to be held across the continent.
The top three leagues will see four teams relegated, meaning that it could be an advantage for teams to be demoted to a weaker division before the second edition, with possible 2022 World Cup places at stake.
League A includes the likes of world champions Germany, reigning European Championship winners Portugal, France and England.
The Netherlands’ 2-0 win in their last 2018 World Cup qualifier against Sweden on Tuesday saw them take the final spot in the top division from Wales, despite failing to reach Russia.
The group matches will be played in September, October and November next year.
The overall Nations League rankings will also be used to decide the seedings for Euro 2020 qualifying.
League A: Germany, Portugal, Belgium, Spain, France, England, Switzerland, Italy, Poland, Iceland, Croatia, Netherlands — one Euro 2020 place on offer
League B: Austria, Wales, Russia, Slovakia, Sweden, Ukraine, Republic of Ireland, Bosnia-Herzegovina, Northern Ireland, Denmark, Czech Republic, Turkey — one Euro 2020 place on offer
League C: Hungary, Romania, Scotland, Slovenia, Greece, Serbia, Albania, Norway, Montenegro, Israel, Bulgaria, Finland, Cyprus, Estonia, Lithuania — one Euro 2020 place on offer
League D: Azerbaijan, Macedonia, Belarus, Georgia, Armenia, Latvia, Faroe Islands, Luxembourg, Kazakhstan, Moldova, Liechtenstein, Malta, Andorra, Kosovo, San Marino, Gibraltar — one Euro 2020 place on offer