What should you do when you forget to recite the Qunut in Witr prayer?
According to the Hanafi school, it is necessary (wajib) to say the qunut (minimally any supplication suffices) in the third cycle (rak`at) of the witr prayer. The place for this is before the bowing (ruku`). [Shurunbulali, Maraqi al-Falah; `Ala al-Din `Abidin, al-Hadiyya al-`Ala’iyya]
If one forgets to make the supplication (qunut), one simply performs the prostrations of forgetfulness (sajda al-sahw) before closing the prayer.
And Allah knows best.
Answered By: Shaykh Faraz Rabbani