If we forget to read Du'a a Qunut in Witr Salah, do we perform Sujud as Sahoo or repeat the Salah?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Qunut Du’a is not obligatory in Witr prayer.  So whoever forgets it does not have to do anything in compensation.  But the Shafi’e prefer that such a person performs the prostrations of forgetfulness if this Witr is in the second half of Ramadan.  The Hanafi believe that it is mandatory on the one who forgets Qunut in Witr to perform the prostrations of forgetfulness. 

The author of ‘Al Ikhtiyar Li Ta’alil Al Mukhtar’ (who is a Hanafi) writes: 'The prostration of forgetfulness is not to be performed for any kind of Zikr except the recitation of the Qur'an in the prayer, the two Tashahhud (after two Rak’ah and at the end of 4 Rak’ah) the Qunut and the Takbeer in the two Eid (Fitr and Adha) because the mentioned forms are obligatory.  Any Zikr apart from these is only Sunnah and does not require that we perform the prostration of forgetfulness for it.'

Allah knows best.