All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The jurists have different opinions in regard to whoever did not pray the pre-Sunnah (supererogatory prayer) of Thuhr until he prayed the obligatory prayer of Thuhr, whether he should pray it after praying the post-Sunnah of Thuhr or before it. Some of them are of the view that he should pray it after praying the post-Sunnah of Thuhr, because ‘Aa’ishah said that “if the Prophet did not pray 4 Rak’ahs before Thuhr, he would pray them after Thuhr.”
Al-Mubaarak Poori said: “After Thuhr means after praying the two Sunnah Rak’ahs after Thuhr.”, because the narration of Ibn Maajah reads “If the Prophet missed the 4 Rak’ahs before Thuhr, he would pray them after the 2 Rak’ahs after Thuhr.”
However, some jurists are of the view that it is to be made up before praying the post-Sunnah of Thuhr, so one prays the 4 Rak’ahs that he missed before Thuhr and then he prays the 2 Rak’ah post-Sunnah of Thuhr. This is the view of the Hanafi and Hanbali schools of jurisprudence.
In any case, the matter is easy, praise be to Allaah, so one may act according to either opinion.
Allaah Knows best.