How can a missed form cost lakhs after PPF maturity?

When a Public Provident Fund (PPF) account matures after 15 years, it doesn't automatically extend with new contributions. To continue depositing money, account holders must submit Form 4 within one year of maturity. Failing to submit this form means any fresh deposits won't earn interest or qualify for Section 80C tax deductions, potentially costing lakhs in lost returns over time.