Every Indian including an NRI is required to file an Income tax return where Total Income exceeds the basic exemption limit of Rs. 2,50,000 for an individual; Rs. 3,00,000 in case of the senior citizen and Rs. 5,00,000 in case of the super senior citizen.
Total Income comprises income from all sources i.e. income from salary, house property, business income, capital gains or any other taxable income. This limit is to be checked before giving the benefit of deductions like 80C,80D, 80DDB etc. You are required to file a return irrespective of whether you have paid tax or not. So, even if the employer has deducted TDS in full you are still required to file an income tax return.