A demat account can have maximum three holders. Proof of identity is to be obtained for all the holders. For First holder proof of correspondence address as well as permanent address is to be obtained in case the correspondence address is not the same as the permanent address.
For joint holders proof of only permanent address is to be obtained. In addition, obtaining PAN Card details of all the holders is compulsory for all categories of demat account holder(s).
U.N. entities/multilateral agencies which are exempt from paying taxes/filing tax returns in India are exempted from the mandatory requirement of PAN. Residents of SIKKIM are also exempted from the mandatory requirement of PAN.
Foreign address and RBI approval details for NRI, FPI or OCB accounts are required in case of NSDL. However this is not applicable in case of CDSL.
In case of CDSL, PIOs falls under the category of Foreign Nationals. In case of NSDL they fall under the category of NRI.
MODELEXAM® 
www.realsoftinfoplan.com