Forgery is defined under Section 463 of Indian Penal Code, Whosoever makes any fake document or incorrect electronic record or part of a document with an intention to cause damage or injury, to the public or to any person, or to support any claim or title, or to cause any person to share with property, or to enter into any express or implied contract, or with purpose to commit fraud or that fraud may be accomplished, commits forgery. Forgery hence can be described as a means to achieve an end- the end is an instance of action or scheme fabricated to mislead someone into believing a lie or inaccuracy.
It is a crime to impersonate another person if harm is caused. False impersonation occurs when someone represents him/herself as another person to deceive others. However, the key element of this offense in most cases is whether an additional act was performed, beyond the deceitful misrepresentation, that: creates a legal or financial liability for the person being impersonated; or benefits the impersonator.
Section 205 of IPC states whoever falsely personates another, and in such assumed character makes any admission or statement, or confesses judgment, or causes any process to be issued or becomes bail or security, or does any other act in any suit or criminal prosecution, shall be punished with imprisonment of either description for a term which may extend to three years, or with fine, or with both.
You must file a police complaint for forgery, fabrication of documents and cheating, as soon as you find out about the situation. It would also be appropriate to write to the inspector-general of registration and the sub-registrar and bring the matter to their notice.
Such cases fall under sections 420 (cheating), 467 (forgery of documents), 468 (forgery for purpose of cheating), 471 (using a forged document as a genuine one) and also 120B (applicable when there is more than one person party to the act), of the Indian Penal Code (IPC).
Reference: Section 205, Section 463, 420, 467, 468, 471 of Indian Penal Code