Teams participating in UEFA's club competitions next season will be able to use new signings who have already played in the tournament for their former sides and make a fourth substitute in extra time.
These changes were among several announced by European football's governing body on Tuesday and they follow decisions made by UEFA's executive committee in February and the game's law-making body, the International Football Association Board, earlier this month.
The decision to let clubs register three new players "without any restrictions" after the group stages, however, may be more controversial, as it effectively ends the idea of being cup-tied.
If the rule was in place this year, Philippe Coutinho would be able to play for Barcelona in the Champions League, despite already featuring for Liverpool.
It also would have helped end ambiguity surrounding the eligibility of Pierre-Emerick Aubameyang and Henrikh Mkhitaryan, who joined Arsenal in January.
Only Mkhitaryan, who joined from Manchester United, has been able to appear in Europa League games while Aubameyang, who moved from Borussia Dortmund, said earlier this month he is "really frustrated" that he cannot.
"This is in line with the existing regulatory situation in the different domestic leagues, which does not impose restrictions on the eligibility for competitions of players registered for a new club during the winter transfer window," UEFA said in a statement explaining its decision to end the "cup tied" rule.
From next season, clubs reaching the Super Cup and the finals of the Champions League and Europa League will be able to have 12 substitutes on the bench -- up from the usual seven.
In the statement, UEFA said this will give "coaches more flexibility regarding substitutes, and facilitate their squad management for the most important fixture of the season."
A fourth substitute in extra time has already been trialled by UEFA in age-group tournaments and is allowed in this season's FA Cup.
The governing body also announced new kickoff times.
Champions League playoffs, group-stage games and knock-out matches will now kick off at 9 p.m. CET, but in the group stages, two of the games on Tuesday and Wednesday will start at 6:55 p.m. CET, apart from on the last matchday, when they will be played simultaneously.
Europa League games will be split between these two kickoff times until the quarterfinals, when they will all start at 9 p.m. CET. The Super Cup will also kick off at 9 p.m. CET.
The split kickoffs may cause headaches for domestic schedules as nobody will want to schedule a game against televised European games. Two years ago, UEFA was annoyed when Manchester United's FA Cup replay at West Ham United was held at the same time as a Champions League quarterfinal, and Barcelona have played a league game in the earlier slot this season.
Another change announced on Tuesday was to allow clubs that have won the Europa League -- or its forerunner, the UEFA Cup -- three times in a row or five times in total to wear a multiple-winner badge on their shirt sleeves.