Eight Pro14, France Top 14 and England Premiership teams will be split into four levels over two pools, with each team playing four group matches, compared to six in the normal season.
The revamped format includes the home and away quarter-finals, with the cumulative score from the two games determining the winner.
The 2019/20 competition, which is now in the quarterfinals, consisted of 20 teams, with the Pro14 providing seven of that number.
The last place in Pro14 for the Champions Cup was decided after a play-off between the two fourth-ranked teams after the South African side of the Cheetahs were omitted.
This year’s expansion paves the way for Connacht, who finished fourth in Conference B, and the Dragons to participate.
Leinster, Ulster and Munster were already assured of qualifying for the elite competition, which is tentatively scheduled for the second weekend in December.
There will be two groups of 12 teams, with the top four of each advancing to the round of 16.
The team that finishes first in Pool 1 will face the fourth team in Pool 2 in the quarter-finals and so on.
The semi-finals and the final of the Champions Cup, which will be played in Marseille on May 22, will be unique matches.
The tournament will be played over eight weekends.
Level 1 teams, which for the Pro14, and most likely the Premiership, will mean the two finalists in each competition, and for the Top 14, the two best-placed teams when their league was canceled, will play at home and at home. ‘away against Tier 4 teams that are not in their respective league.
This means that Bordeaux-Bègles and Lyon form the Tier 1 teams of France, unless Clermont or Racing 92 win this season’s competition.
Likewise, if Leinster, for example, lost to Munster on Friday but won the Champions Cup outright, he would occupy the rank 1 spot of the defeated finalist in the decision maker Pro14.
For example, if Leinster and Ulster qualified for the Pro14 final, they would constitute Tier 1 of Pro14, be placed in separate pools and play against the French and English Tier 4 teams from the same pool.
Guinness Pro14 confirmed to RTÉ Sport that their finalists will be the level 1 teams and that clubs that did not make the semi-finals will be seeded according to their league positions after round 13, which was before closing.
Level 2 and 3 teams compete in the group stage, once again avoiding any team from the same national competition.
“The EPCR Board of Directors has unanimously agreed that new Heineken Champions Cup and Challenge Cup tournament formats will be introduced for the 2020/21 season,” said European Professional Club Rugby.
“The decision to change the formats for next season on an exceptional basis was taken against the backdrop of the Covid-19 public health crisis and its continued impact on professional club play in Europe.
“With an extended knockout stage and no repetitions of domestic matches during the group stage, this format creates whole new competitive opportunities for Europe’s elite clubs and their supporters. ”
The 2020/21 Challenge Cup will start with 14 clubs – six from the Top 14, four from the Premiership and four from the Pro14 – in a single pool, while the eight clubs that finish outside the Champions Cup quarter-finals advance to the round of 16 of the Challenge Cup.
The EPCR has also confirmed that there is no limit to the number of non-EU players in the matchday squads for the tournament.
CLUBS QUALIFIED FOR THE 2020/21 HEINEKEN CHAMPIONS CUP
December 14: Leinster Rugby, Edinburgh Rugby, Munster Rugby, Ulster Rugby, Scarlets, Glasgow Warriors, Connacht Rugby, Dragons (rankings to be confirmed at the end of the current season)
Top 14: Bordeaux-Bègles, Lyon, Racing 92, RC Toulon, La Rochelle, ASM Clermont Auvergne, Toulouse, * Montpellier or Castres Olympique
Follow the Pro14 semi-final between Leinster and Munster (7:35 p.m. Friday) with our live blog on RTÉ Sport Online and the RTÉ News app or listen to live commentary on RTÉ Radio 1.
Follow the Pro14 semi-final between Edinburgh and Ulster (7:35 p.m. Saturday) with our live blog on RTÉ Sport Online and the RTÉ News app or listen to live commentary on RTÉ Radio 1 Extra.