Prayer: Forgetting a Sajdah or Tashahhud and Remembering During or After Rukuʿ
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1231
If a person remembers in rukūʿ or after it that he has forgotten one sajdah or tashahhud from the previous rakʿah, he must make up the sajdah after the salām of the prayer [for the forgotten sajdah]; and for [the forgotten] tashahhud, he must perform sajdatā al‑sahw.