The 2021 Campeonato Paulista de Futebol Profissional da Primeira Divisão - Série A1 was the 120th season of São Paulo's top professional football league. The competition was played from 28 February to 23 May 2021.
In addition, it was also decided that Paulistão 2021 will have VAR in all games, including those in the first phase of the competition.
The teams are ranked according to points (3 points for a win, 1 point for a draw, 0 points for a loss). If two or more teams are equal on points on completion of the group matches, the following criteria are applied to determine the rankings:
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The Troféu do Interior of the 2021 Campeonato Paulista began on 12 May with the quarter-finals and ended on 20 May 2021 with the final. A total of six teams compete in the Troféu Interior.
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Note: The match was concluded the following day, due to a power outage at the stadium.
The knockout stage of the 2021 Campeonato Paulista began on 11 May with the quarter-finals and end on 23 May 2021 with the final. A total of eight teams compete in the knockout stage.
The quarter-finals will be played in a single match at the stadium of the better-ranked team in the first phase. If no goals were scored during the match, the tie will be decided via a penalty shoot-out. The semi-finals will be played with the same format as the quarter-finals. The finals will be played over two legs, with the team having the better record in matches from the previous stages hosting the second leg.
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