Income tax liability applies to every person, including natural and artificial entities, under the statutory definition. Income-tax liability attaches to every person as defined under the statute (section 2(3) in the text), covering both natural and artificial entities. The definition of person includes Individual, Hindu Undivided Family, Association of Persons, Body of Individuals, Firms, LLPs, Companies, Local Authorities and any other artificial juridical person not otherwise classified, so that artificial entities as well as individuals are liable to pay income-tax.