2- Omissions in Salah(rukn/wajib/sunnah)> 2a- omission of Rukn (pillar)
then depends when you remembered the omission of the rukn... so whatever the case maybe in the 'make up' ra'kah one should recite the tashahud in it then followed by a sujood as sahw after the tasleem.
Shaikh Muhammad ibn Saalih al-Uthaimeen rahimahullah has a treatise named "Sajdatus-Sahw" .One may refer this book for more detail about Sujood as sahw.
And Allah knows best..
Abu Bakr Al-Siddiq Radhiyallahu anhu said: I will not leave anything Allah's Messenger Sallahu alihi wa ssallam did, except that I will also do it; for I fear that if I were to leave any of his commands and ways I would deviate.(Al-Bukhari, Al-Sahih 2:386
if i pray 3 rak'ah for maghrib, but i forget to recite surat ul-fatiha in my 3rd rak'ah for example, or i miss out any other pillar, i would have to make up one rak'ah after the tasleem...
so in this "make up" rak'ah, am i supposed to recite the tashahhud? Or do i just make tasleem after sitting from the sujud...
please post here if any of you find any statements from the scholars about this... barakAllahu feekum