Once an assessee becomes a non resident he cannot operate Savings account in India as per the FEMA regulations.
He is compulsorily required to convert his resident account in either NRO/NRE account once he becomes a non resident.
NRO/NRE account can be either Saving or current account as per assessee discretion . However the assessee is required to maintain an average monthly balance of 75000 (NRE account)/ 25000(NRO account). The limit may differ from Bank to Bank.
Main differences between NRO and NRE account:
NRE account is freely repatriable (both principal and interest) whereas the NRO account has limited repatriability (As per FEMA regulations)in a particular financial year. However, CA certifications will be required for the same.
Income earned via NRE account is exempt from taxation. However, interest earned w.r.t. NRO account is taxable.
NRE account can be jointly owned with Non-resident but not with resident Indian. However, NRO account can be jointly owned with Nonresident and resident Indian.