Inadvertent omission of a wajib can require sujud al-sahw. Omitting an ordinary Sunnah or recommended act does not by itself do so.
For example, forgetting a routine recommended formula is not equivalent to omitting tashahhud, a separately identified binding obligation.
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Prostrations of Forgetfulness: Causes, Method, Missed Sittings and Doubts
Inadvertent omission of a wajib can require sujud al-sahw. Omitting an ordinary Sunnah or recommended act does not by itself do so.
For example, forgetting a routine recommended formula is not equivalent to omitting tashahhud, a separately identified binding obligation.