Firstly: Missing an Integral of Prayer Forgetfully
Whoever forgetfully misses an integral of prayer – other than the opening Allahu Akbar – must perform it and everything that follows it unless the proper place of its performance has passed.  Though they differ regarding at which point one can no longer make up the missed integral. This is the position of the majority: the Malikis, Shafi`is, and Hanbalis.
Secondly: The Ruling of the Prostration of Forgetfulness for Missing an Integral
Whoever misses an integral of prayer – such as bowing or prostrating – must perform it. The prostration of forgetfulness does not make up for it. Consensus on this was related by Ibn `Abd al-Barr.
Thirdly: The Ruling of the Prostration of Forgetfulness for Missing a Wajib Act
It is wajib to perform the prostration of forgetfulness whenever a wajib act of prayer is omitted forgetfully.  Though those who hold this opinion differ on what the wajib acts of prayer are. This is the position of Hanafis, Hanbalis, Ibn Baz, and Ibn `Uthaymin.
Fourthly: The Ruling of the Prostration of Forgetfulness for Missing a Sunnah Act
The prostration of forgetfulness is legislated for one who misses a sunnah act of prayer, but it is not wajib. This is the position of the Hanbali school. It is the position of choice of Ibn Baz and Ibn `Uthaymin.