The World Federation One Stop Fiqh

Ruling 1218

If in ṣalāt al-iḥtiyāṭ one forgets tashahhud or one sajdah and it is not possible to perform them at their correct time, the obligatory precaution is that after the salām of the prayer he must make up the sajdah; however, it is not necessary for him to make up the tashahhud.