The rescheduling of the 2020-21 tournament forced by the coronavirus pandemic means the first three qualifying rounds will consist of single-leg fixtures, with the home team decided by the luck of the draw.
Uefa have now published the revised regulations for their flagship club competition which state that those one-off ties will be played to a finish with extra-time and penalties.
The away goals rule will return for the final play-off round which reverts to the traditional two-legged knockout tie format.
Scottish champions Celtic are certain to be among the top seeded clubs in each of the first three qualifying rounds.
Neil Lennon’s squad will discover their first round opponents when the draw is made on 9 August, with the tie scheduled for 18 or 19 August.
Among the sides they could face are Swedish champions Djurgardens, Buducnost Podgorica of Montenegro and Belarussian champions Dynamo Brest.