Ab Initio Meaning and Origin
Ab Initio is a legal phrase of Latin origin. Ab means ‘from’ and Initio means ‘start or beginning’ and hence the phrase literally means, from the very beginning.
If a case is declared by the court as that of ab initio, then the decision of the court, in that case, is deemed to be applicable from when the act was occurred and not when the ruling or decision came into effect.
We often come across the term void ab initio which is derived from the phrase ab initio. An agreement or deed is said to be void ab initio if it is not legally valid at any point. It is treated as if it never existed. It is applicable in matters such as marriage, contracts and property.
A, a minor enters into an agreement with B for buying a particular property. B transfers the property in his name but A fails to make the payment. B cannot sue A for the non-payment since the agreement is void ab initio.
Aradhaya marries Rahul in 2004. Due to marital issues, the couple starts living separately without any legal divorce. In 2012, Rahul marries Shashi while the first wife is still alive. The second marriage is not valid and hence deemed to be void ab initio.
X, the sheriff of the court enters the property of Y under the order of the court in order to seize an expensive painting. While in the course of executing the court orders, the sheriff also takes a valuable marble scripture from the property. He is said to have abused the authority of the court and is deemed to be a trespasser ab initio.
Important Case Laws
In the case of Mohiri Bibi v. Dharmodas Ghose, a mortgage deed was entered into by the parties when one of them was minor and hence it was held by the Privy Council that the agreement is void ab initio since the minor party is competent to enter into such a deed.
In the case of Radhe Shyam Gupta v. UP State Agro Industrial Corporation, it was held that if an order is declared as void ab initio, it implies that the order never existed.
 (1903) ILR 30 Cal. 539 (PC).
 Writ Petition No. 1591 of 1981.