A person residing in India for income tax purposes must report her entire global income in India's tax return.
However, an NRI must report only that income in India earned or received in India. If the gross total income of a person in any year exceeds ? 2.5 lakh, and he/she is based in India, then they must file ITR.
His/her income is below the taxable limit and yet TDS (tax deducted at source) has been cut on it (for example, if a bank has deducted TDS on interest income on deposits), they must claim a refund.
A refund may only be claimed by filing an ITR. Those who want to report earnings (or loss) from capital assets and do not have any income (or loss) from a business or occupation must file ITR-2.
At the same time, if a person is a resident in India and has paid taxes abroad, tax relief may be available even though no DTAA agreement exists.