Tawaf Al-Ifadah is the Tawaf performed by the pilgrim on the 10th of Dhul-Hijjah as the last formal rite of Hajj in Makkah after changing into street clothes. It is one the rituals of Hajj and if it is missed, the Hajj is void.
In this regard, we cite what Sheikh Sayyed Sabiq states in his well known book Fiqh As-Sunnah:
There is a consensus among Muslims that Tawaf Al-Ifadah is one of the essentials of Hajj, and if someone fails to observe it his Hajj is void. The Qur’an says: (Then, let them complete the rites prescribed for them, perform their vows, and (again) circumambulate the Ancient House) (Al-Hajj 22:29).
According to Ahmad, a pilgrim must make a definite intention for its performance. All the other three imams hold that having the intention to perform Hajj covers and applies to all its rites including Tawaf Al-Ifadah.
The majority of scholars holds that Tawaf Al-Ifadah comprises seven rounds of the Ka`bah. Abu Hanifah, however, is of the view that only four of the seven rounds are essential in Hajj, and if these (four) are missed the Hajj of a person becomes void. The remaining three rounds are necessary (wajib) but not essential. A pilgrim abandoning one or all of these three rounds misses a necessary part, but it does not invalidate his Hajj, although he is required to offer a sacrifice of an animal in atonement for it.