Yes, you can apply RTI to Hindustan Copper Limited (HCL).
Hindustan Copper Limited (HCL) a Government-owned Corporation in the Central Public Sector Enterprise under the Ministry of Mines (India), Government of India. Thus, HCL is a Public Authority as per Section 2 (h) of the RTI Act 2005 and comes under the ambit of the Act.
Hence, you can apply RTI to Hindustan Copper Limited (HCL) by paying the prescribed fee either Online or by Offline mode.
To know, further procedure for filing RTI's Online for Central Government please refer https://onlinerti.com/how-to-file-rti-online-for-center
