The Public Provident Fund (PPF) is one of the most commonly recommended long-term savings instruments in India, but the recommendation usually stops at "it's safe and tax-free" without explaining how the account actually behaves over its lifetime. The mechanics matter, because they shape when and how you should be putting money in.
Interest compounds annually, but is calculated monthly
PPF interest is calculated every month based on the lowest balance in your account between the 5th and the last day of that month, but it's only credited to your account once a year, at the end of the financial year. That monthly-lowest-balance rule is the part people miss: if you deposit after the 5th of a month, that deposit doesn't earn interest for that month at all. Depositing before the 5th, especially early in the financial year, meaningfully increases the interest your money earns over 15 years.
The 15-year lock-in isn't just a suggestion
A PPF account has a mandatory 15-year tenure from the end of the financial year in which it was opened. You can't withdraw the full balance before that, though partial withdrawals are permitted from the 7th year onward under specific conditions. This lock-in is the tradeoff for the rate and the tax treatment -- it's built for retirement-horizon or long-term goal money, not funds you might need access to in three years.
Extending beyond 15 years
At maturity, you're not forced to close the account. You can extend it in blocks of 5 years, either continuing to contribute or letting the existing balance keep earning interest without adding more. This is how a lot of long-term PPF balances end up compounding for 20-25+ years rather than stopping at 15.
Why it's called "EEE"
PPF is one of the few instruments with Exempt-Exempt-Exempt tax treatment: contributions (up to the annual limit) qualify for deduction, the interest earned is tax-free, and the maturity amount is tax-free too. Compare that to a fixed deposit, where the interest is taxed as income every year, and the compounding advantage becomes clearer -- your PPF balance keeps growing on the full interest amount, not on what's left after tax.
There's an annual contribution ceiling
You can't deposit unlimited amounts. There's a maximum you're allowed to contribute per financial year, and contributions beyond that limit don't earn interest. This caps how much of your portfolio PPF alone can realistically carry, which is why it usually sits alongside other instruments rather than being the only savings vehicle.
Running the numbers
Because the annual compounding and the timing of deposits both affect the final maturity value, it's worth actually calculating rather than estimating. The PPF Calculator works out your maturity amount over the 15-year term based on your contribution amount and the applicable interest rate.