Sehev during Namaz

Situations where namaz is not accepted and should be prayed once again.

1. When one forgets to recite Takbirat ul Ehram

2. When one forgets to recite Surat ul Fateha (al Hamd)

3. When one forgets to perform ruku’

4. When one prays an extra rak’at without reciting mhoto tashahud. (e.g. 5^th rak‘at in Zuhur, 4^th rak‘at in Maghrib)