The World Federation One Stop Fiqh

Ruling 1207

If after performing ṣalāt al-iḥtiyāṭ one realises that the deficiency in the number of rakʿahs in his prayer was more than the number of rakʿahs in his ṣalāt al‐iḥtiyāṭ – for example, for the doubt between three and four rakʿahs, he performs one rakʿah of ṣalāt al‐iḥtiyāṭ and later realises that he had performed two rakʿahs – then, in the event that after performing ṣalāt al‐iḥtiyāṭ he did something that invalidates prayers, such as turning his back to qibla, he must perform the prayer again. However, if he did not do anything that invalidates prayers, the obligatory precaution is that he must perform the prayer again, and he must not suffice with joining one rakʿah to the prayer.