If ṣalāt al‑iḥtiyāṭ and sajdatā al‑sahw become obligatory for a person, he must first perform ṣalāt al‑iḥtiyāṭ. The same applies, based on obligatory precaution, if ṣalāt al‑iḥtiyāṭ and making up a sajdah become obligatory for a person. Ruling 1220.* The rule concerning suppositions (ẓann) in the number of rakʿahs in obligatory prayers is the same as the rule concerning certainty; and based on obligatory precaution, this also applies to nāfilah prayers.
For example, if someone does not know whether he has performed one or two rakʿahs but has a supposition that he has performed two rakʿahs, he must assume he has performed two rakʿahs. If in a four rakʿah prayer he has a supposition that he has performed four rakʿahs, then performing ṣalāt al‑iḥtiyāṭ is not necessary. As for acts of prayers, the rule concerning suppositions is the same as that for doubts.
Therefore, if one has a supposition that he has performed rukūʿ, then in case he has not gone into sajdah, he must perform rukūʿ. If he has a supposition that he has not recited Sūrat al-Ḥamd, in the event that he has started to recite the other surah, he must dismiss his supposition and his prayer is valid.