An AOP (Association of Persons) is not defined in the Indian laws. General Clauses Act, 1897 has not defined an AOP directly but, while defining person, it also includes association.
Section 2(31) of the Income-tax Act, 1961 also has not defined AOP, but given similar treatment to AOP the way General Clauses Act has given. An AOP is formed by relation between parties. It may be a consortium or joint venture registered or unregistered. Since association of persons is not defined, the meaning has to be understood from the meaning assigned to the term by the Supreme Court which observed in the case of
CIT vs. Indira Balkrishna (39 ITR 546) that an association of persons, must be one in which two or more persons join in a common purpose or common action and the association must be one the object of which is to produce income, profits or gains.