The format and schedule of the UEFA Nations League was formally approved by the UEFA Executive Committee on 4 December 2014. According to the approved format, the 55 UEFA national teams were divided into four divisions (called "leagues"): Each league was divided into four groups of three or four teams, so each team played four or six matches within their group (using the home-and-away
round-robin format), on double matchdays in September, October and November 2018. In the top division, League A, teams competed to become the UEFA Nations League champions. The four group winners of League A qualified for the Nations League Finals in June 2019, which was played in a knockout format, consisting of the semi-finals, third place play-off, and final. The semi-final pairings, along with the administrative home teams for the third place play-off and final, were determined by means of an open draw on 3 December 2018. Host country Portugal was selected among the four qualified teams on 3 December 2018 by the UEFA Executive Committee, with the winners of the final crowned as the Nations League champions. Teams also competed for
promotion and relegation to a higher or lower league. In each league, the four group winners (except League A) were promoted, while the last-placed teams of each group (except League D) were initially to be relegated; the exception was in League C, where due to different-sized groups, the three fourth-placed teams and the lowest-ranking third-placed team were initially to be relegated. However, due to a revamp of the format for the 2020–21 UEFA Nations League, no teams were eventually relegated, and some second-placed and third-placed teams were also promoted. ==Tiebreakers==