Under the Post Office Senior Citizen Scheme, if your annual interest exceeds Rs 50,000, TDS will apply. However, if the interest earned is less than Rs 5,00,000 annually, no tax is payable. For example, if you invest Rs 5 lakh annually, in 5 years the total amount will grow to Rs 7 lakh 5 thousand, with Rs 2,05,000 being the interest amount subject to TDS.