Ruling 1246
If a person knows he has forgotten to perform a sajdah but doubts whether or not he remembered before performing rukūʿ of the next rakʿah and then performed it, the recommended precaution is that he should make it up.
Prayer: Doubting Whether a Forgotten Sajdah Was Performed Before Rukuʿ
Practical Laws of Islam as per the teachings of Ayatullah Sistani
