Qaḍāʾ prayers can be performed in congregation, irrespective of whether the prayer of the imam of the congregation is a qaḍāʾ or adāʾ prayer; and it is not necessary that both the follower and the imam perform the same prayer. For example, there is no problem if a follower performs qaḍāʾ ṣubḥ prayers with the ẓuhr or ʿaṣr prayers of the imam.