FOREIGN VISITORS When Visiting India : RIGHTS AND RESPONSIBILITIES

No person may enter Indian borders without a proper passport and valid Indian Visa.
After landing at Indian shores, every foreigner should register himself with the concerned Foreigner’s Registration Officer within a period of 15 days. However, a foreign citizen visiting India on a tourist visa and intending to stay in India for a period of 180 days or less, does not need to get registered.
If for some unavoidable reasons, a foreign citizen requires an extension for his stay in India, he should apply for the same, at least 2 months prior to the expiry of the valid period of his stay in India, to the Office of the Foreigner’s Registration Officer i.e. Deputy Commissioner of Police (Special Branch).
Following documents, in triplicate, should be furnished along with such application:

(1) Application for extension of time limit, in the prescribed format
(2) Copy of the passport.
(3) Copy of the Indian Visa.
Courtesy: https://mumbaipolice.maharashtra.gov.in/foreign_visitors.asp