Assalamualaikum, is Sujood as Sahw applicable to Sunnah prayers if we make mistakes?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The basic principle is that a person performing a voluntary prayer should perform the Prostration of Forgetfulness, just as it is prescribed for someone performing an obligatory prayer when its cause exists. Imam Al-Bukhari said: In the Chapter (Forgetfulness in Obligatory and Voluntary Prayers): “And Ibn Abbas performed two prostrations after his Witr prayer.”

In Musannaf Ibn Abi Shaybah it is narrated from Abu Al-‘Aliyah Al-Bara’, may Alalah have mercy upon him, from Ibn Abbas who said: “I saw him perform two prostrations after his Witr prayer.”

The following scholars also held the view that the prostration of forgetfulness applies in voluntary prayers: Al-Hasan Al-Basri, Sa’id ibn Jubayr, Qatadah, Al-Thawri, Malik, Al-Awza’i, Al-Shafi’i, and Ahmad ibn Hanbal . However,Ibn Sirin did not hold this view. This was reported by Ibn al-Mundhir in Al-Ishraf.

However, some scholars believe that not every reason that requires the prostration of forgetfulness in obligatory prayer also requires it in voluntary prayer, and the detailed discussion of this is extensively explained in the books of jurisprudence.

Allah Knows best.