How is the recitation of the rak'ah repeated after an error in Al-Fatihah: Is it after the taslim or before the taslim by performing another rak'ah?

If the worshiper does not remember the mistake in Al-Fatihah until after completing the unit (rak'ah) in which the mistake occurred, then this unit is considered void, and the subsequent units take its place in the sequence. If he does not remember the mistake until after the salutation (tasleem), then he performs the opening takbeer (takbeerat al-ihram) again and offers a unit, provided the interval is not long. Otherwise, the prayer becomes invalid, and it becomes obligatory to repeat it.