The World Federation One Stop Fiqh

Ruling 745

If a person doubts during the ʿaṣr prayer whether he has performed the ẓuhr prayer or not, he must complete the prayer with the intention of the ʿaṣr prayer and thereafter perform the ẓuhr prayer. However, if the time is so little that after completing the prayer the sun will set and there will not be enough time remaining to perform even one rakʿah, it is not necessary to make up the ẓuhr prayer afterwards.