PPF Interest Calculation 2026: Why the 5th of the Month Rule Can Cost You Thousands

Most PPF holders know the headline rate — 7.1% for the October-December 2026 quarter — but far fewer know that when you deposit inside a month decides whether you actually earn that rate on the money for that month at all. PPF interest isn't calculated on your deposit date or your annual total. It's calculated on the lowest balance sitting in your account between the 5th and the last day of every calendar month, and one deposit slip filed two days late can quietly cost you a month's interest — every single year you repeat it.

How PPF Interest Is Actually Calculated

Under the PPF Scheme rules, interest for each calendar month is computed on the lowest balance in your account between the close of the 5th day of that month and the last day of that month. That monthly interest figure isn't paid out monthly — it's added up across all 12 months and credited to your account in one shot at the end of the financial year, on March 31. The practical effect: a deposit sitting in your account on the 5th earns interest for that entire month, while the exact same deposit made on the 6th earns nothing for that month, because it wasn't there to be counted at the checkpoint.

The Real Cost If You Do This Every Year

Missing the 5th once costs roughly one month's interest on that deposit — not dramatic on its own. The problem is that most PPF holders who miss it once tend to miss it every year, since it's a habit, not a one-off slip. Run that ₹887-a-year shortfall through 15 years of compounding, on a saver who deposits the full ₹1.5 lakh every year but always a few days after the 5th instead of before it, and the gap in the final maturity corpus works out to a little over ₹22,000 — money lost purely to timing, not to any choice about where the money was invested.

Lump Sum vs Monthly Deposits: The Rule Applies Differently

A lump-sum depositor only has one date in the entire year that matters — the day the full ₹1.5 lakh goes in. Get that inside the April 1-5 window and the whole year's interest on the whole amount is locked in from month one. A monthly depositor faces this same 5th-of-the-month checkpoint twelve times over, and each missed month independently loses interest only on that month's instalment, not on the running balance already in the account. Spreading deposits across the year but consistently missing the 5th is a smaller loss per month than a lump-sum miss, but it repeats twelve times instead of once, and the two effects land in a similar range by year-end.

• Lump-sum depositors: deposit between the 1st and 5th of April to earn a full year's interest on the full amount
• Monthly depositors: each instalment must clear by the 5th of that month to count toward that month's interest
• Interest is credited only once a year, on March 31 — but it's calculated month by month all year
• A deposit on the 5th itself is safe; the cutoff is the close of the 5th, not before it

What Multiple Deposits in the Same Month Change

The rule only cares about the lowest balance the account held between the 5th and month-end — not how many separate deposits built up to that balance. If you deposit ₹50,000 on the 2nd and another ₹50,000 on the 4th, both are in by the checkpoint and both earn that month's interest on the combined ₹1 lakh. The Public Provident Fund Scheme also caps deposits at 12 per financial year, alongside the overall ₹1.5 lakh annual ceiling and a ₹500 minimum to keep the account active — so there's no benefit to breaking a lump sum into more instalments than that inside a single month; it only adds paperwork for the same interest outcome.

This timing rule is worth building into your broader 80C planning, not just your PPF routine — our NSC vs PPF vs ELSS comparison covers how PPF stacks up against the other two popular ₹1.5 lakh options if you're deciding where the money should go in the first place. If you're an NRI wondering whether your existing account still earns this rate at all, our PPF for NRIs guide covers the accounts that no longer do. And once the account is running, our PPF withdrawal rules guide and PPF calculator cover accessing the money early and projecting your maturity value, while our NPS vs PPF comparison covers how PPF fits next to your other retirement instruments. If you're still deciding whether PPF or a bank FD suits your goal in the first place, our PPF vs Fixed Deposit comparison walks through the post-tax math this 5th-of-the-month rule feeds into. And if you haven't opened the account yet, our guide to opening a PPF account online versus at a post office covers exactly what each route involves before this timing rule even applies to you.