Between September and November, each team in the Nations League will face every other team in their group twice; once at home and once away.
In League A, the top two teams from each group will make the quarter-finals later in that campaign. A knockout tournament between those eight teams will then play out to determine the overall Nations League winner.
In Leagues B, C and D, each group winner will be promoted up one league.
The teams finishing bottom of their groups in Leagues A, B and C will be relegated down one league.
Teams finishing second in groups from Leagues B, C and D will enter play-offs against teams that finish third in Leagues A, B and C in relegation play-offs.
The March international break in 2027 will see the quarter-finals from League A and the relegation play-offs between League A/B and League B/C take place.
The semi-finals and final for the Nations League campaign will take place in the international break of June 2027, as will the League C/D play-off.
The best-performing teams in the Nations League that do not qualify for the 2028 European Championships from the qualification campaign will enter to play-offs to earn the final qualifying spots for the tournament.