PPF: Lump sum or monthly deposits for higher returns?

Investing Rs 1.2 lakh annually in a lump sum before April 5 in India's Public Provident Fund yields approximately Rs 99,000 more than monthly deposits of Rs 10,000 over 15 years, based on the current 7.1% interest rate. The lump sum method generates a maturity amount of Rs 32,54,568, while monthly investments yield Rs 31,55,680, with both requiring a total investment of Rs 18,00,000. Interest is calculated on the lowest balance between the 5th and last day of each month. The PPF scheme offers triple tax exemption under the old tax regime, allows partial withdrawals from the 7th financial year, and can be extended in 5-year blocks after maturity.