Earlier, the facility was available till June 30, 2017.
"The Home Ministry has decided to extend the date for submission of the application for registration as OCI card holder by the erstwhile PIO cardholders till December 31, 2017," an official said.
This was for the fourth time the date for conversion of PIO cards to OCI cards has been extended since March 31, 2016.
The PIO card was first implemented in 2002 as a benefit to foreign nationals who could establish at least a third generation tie to Indian origin. The PIO card was valid for travel, work, and residence in India for a period of 15 years.
The OCI card was implemented in 2005, carried more expansive benefits than the PIO card, and was valid for the holder's lifetime.
Prime Minister Narendra Modi had announced in 2014 that the PIO and OCI cards would be merged and the Indian diaspora would be given maximum possible benefits.
Simultaneous existence of PIO and OCI cards led to confusion among People of Indian Origin residing abroad, officials said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)