Powers of attorney in India sit at the intersection of three statutes. The Powers of Attorney Act, 1882 supplies the basic definition and, through Section 2, lets the attorney do anything in their own name that is authorised, with the act binding the principal. The law of agency in Chapter X of the Indian Contract Act, 1872 governs the substance of the relationship, the attorney's duty of good faith, the limits of authority, and crucially the rules on revocation and termination found in Sections 201 to 210. The Registration Act, 1908 and the relevant Stamp Act (the central Indian Stamp Act, 1899 or the applicable State enactment) determine the formalities that make the instrument usable.
Execution is what gives the document weight. The principal must sign, ideally before two witnesses, and the instrument should be written on non-judicial stamp paper of the value prescribed by the State, which varies considerably. Under the Indian Evidence Act, 1872, a power of attorney signed before a notary public is presumed to have been validly executed, which is why notarisation is standard practice and essential for any instrument signed outside India. For an NRI, the document is attested by the Indian Consulate or a local notary, then must be stamped in India within three months of receipt under the Stamp Act.
The single most important rule concerns property. Following the Supreme Court's decision in Suraj Lamp & Industries Pvt. Ltd. v. State of Haryana (2012) 1 SCC 656, a power of attorney cannot transfer title to immovable property. The so-called "GPA sale" used to dodge stamp duty is dead; a registered sale deed is the only route to valid ownership transfer. A POA can still authorise your attorney to sign that sale deed, but where the instrument deals with immovable property it must itself be registered before the Sub-Registrar under Section 17 of the Registration Act, 1908. The official text of the governing statute is available through the India Code repository of the Powers of Attorney Act 1882.