POMIS Interest & Formula Explained with Examples

Many Indian savers open a Post Office Monthly Income Scheme account without ever understanding the maths that decides their payout. Yet the formula is one of the easiest in personal finance, and knowing it helps you verify every rupee the post office pays you. This article breaks down the POMIS interest formula in plain language, explains why it uses simple interest rather than compounding, and works through several examples in rupees.

Understanding the mechanics matters because it changes how you compare the scheme with alternatives. Once you see exactly how the interest is produced each month, you can judge whether the scheme suits your goals or whether a compounding product such as a bank fixed deposit would serve you better over the same five years.

Expert insight: The defining feature of the POMIS formula is that it never touches your principal. The same amount you deposit is the same amount returned at maturity, and every month you simply receive the interest that principal has generated.

The Core POMIS Formula

The scheme pays simple interest on a fixed principal, so the monthly income calculation is a single short equation. The post office MIS interest formula is:

Monthly Income = (Principal x Annual Interest Rate) / 12

Here the principal is your one-time deposit, the annual interest rate is currently 7.4%, and dividing by twelve converts the yearly interest into the monthly payout. There is no exponent, no compounding factor and no reinvestment term, which is precisely why the calculation stays so approachable for first-time investors and senior citizens alike.

Why POMIS Uses Simple Interest

Compound interest grows your money because each period’s interest is added back to the principal and then itself earns interest. POMIS deliberately avoids this because the whole point of the scheme is to hand you a regular income rather than to build a larger corpus. Since the interest leaves the account every month and is paid to you, there is nothing left inside to compound. This is a genuine trade-off: you gain a dependable monthly cash flow but forgo the exponential growth that a reinvesting product would deliver over the same period.

How the Interest Rate Is Set and Locked

The rate is not fixed forever across the market. The Ministry of Finance reviews small savings rates every quarter, so the headline figure can change for new accounts opened in a future quarter. However, the rate that applies to your account is the one prevailing on the day you open it, and that figure is then locked for your entire five-year tenure. This gives POMIS a valuable certainty: a fall in market rates cannot reduce your income once your account is running, which is a meaningful comfort for retirees planning fixed monthly expenses.

Worked Examples in Rupees

Let us run the formula across three deposit sizes so the pattern becomes clear.

Example 1 – 6 lakh single account: 6,00,000 x 0.074 = 44,400 a year. Divided by 12, that is 3,700 rupees each month, and 2,22,000 in total interest over five years.

Example 2 – 4.5 lakh single account: 4,50,000 x 0.074 = 33,300 a year, which is 2,775 rupees a month. This is a common choice for a single senior citizen who wants a moderate supplement.

Example 3 – 15 lakh joint account: 15,00,000 x 0.074 = 1,11,000 a year, or 9,250 rupees a month, the maximum the scheme allows.

How Taxation Fits the Formula

The formula tells you the gross interest, but your take-home figure depends on tax. POMIS interest is added to your total income under the head income from other sources and taxed at your slab rate. Unlike a bank deposit, the post office does not deduct TDS, so the full calculated amount is credited to you and you must set aside the tax yourself. A retiree in the zero-tax bracket keeps the entire payout, while a working investor in a higher slab effectively earns a lower post-tax return, which is worth factoring into any comparison.

Benefits of Understanding the Formula

Grasping the formula turns you into an informed investor rather than a passive one. You can instantly check whether the amount credited each month is correct, plan the deposit needed for a target income, and compare the scheme fairly against compounding products. It also helps you explain the scheme to elderly relatives, who often rely on POMIS but may not know how their income is produced. This clarity reduces the chance of being misled and builds genuine confidence in your financial decisions.

Challenges and Limitations

The simple-interest design that makes POMIS easy also caps its long-term wealth creation, so it is better for income than for growth. The taxable nature of the interest can meaningfully reduce returns for higher earners, and the 9 lakh single-account ceiling limits how much income any one person can draw. Because the rate is reset quarterly for new accounts, timing your entry matters, and a saver who opens an account just before a rate cut is fortunate while one who opens just after enjoys a lower locked rate for five full years.

Common Mistakes to Avoid

• Confusing simple with compound interest. Some savers expect their corpus to grow, but POMIS pays out interest rather than reinvesting it.
• Using an outdated rate. Always calculate with the current quarter’s rate, since the figure can change for new accounts.
• Forgetting the tax step. The formula gives gross interest; the net amount after slab tax can be noticeably lower.
• Overlooking the deposit ceiling. Plugging a figure above 9 lakh into the formula gives an income you cannot actually receive in a single account.
• Assuming monthly compounding. There is no monthly compounding, so do not apply a compound-interest formula to this scheme.

Best Practices and Expert Recommendations

• Verify each credit against the formula. A quick monthly check ensures the post office has paid you correctly.
• Calculate the post-tax figure. Apply your slab rate to the annual interest so you know your true return before investing.
• Open when rates are attractive. Since your rate locks for five years, opening during a higher-rate quarter maximises your income.
• Pair with a compounding product. Direct your monthly payout into a recurring deposit or SIP to regain some growth.
• Keep documentation. Record your principal, rate and opening date so the calculation is easy to reproduce at tax time.
• Review at maturity. Recalculate with the prevailing rate before reinvesting, as it may differ from your original rate.

The POMIS formula proves that safe investing does not have to be complicated. With one short equation you can predict your income, verify your payouts and plan your finances for the full five years with genuine confidence.

POMIS Versus a Compounding Deposit Over Five Years

To appreciate the trade-off in the simple-interest design, compare a 6 lakh POMIS account with a hypothetical product that compounds at the same 7.4% and pays nothing until maturity. In POMIS you receive 3,700 rupees every month, adding up to 2,22,000 across five years, and your 6 lakh is returned intact. A compounding product paying at maturity would instead grow the 6 lakh to roughly 8.6 lakh, a gain of about 2,60,000, because each year interest earns further interest. The compounding option produces more total wealth, but it gives you nothing to live on in the meantime. This is the heart of the choice: POMIS trades a slightly lower total return for a dependable monthly cash flow, which is exactly what income-seekers and retirees value most. Neither approach is universally better; the right one depends entirely on whether your priority is spending money now or growing money for later. Many disciplined savers even bridge the gap by reinvesting each POMIS payout, partially recreating compounding while still keeping the safety and simplicity of the scheme.

Seeing the two side by side also clarifies why POMIS should not be judged purely on headline returns. Its value lies in predictability and liquidity of income, not in maximising the final corpus, so comparing it only against compound growth misses the point of the product.

If you want to go further, our companion guide explains the full POMIS calculation in detail with additional worked examples you can follow at your own pace.

Frequently Asked Questions

What is the exact POMIS interest formula?
The formula is Monthly Income equals Principal multiplied by the annual interest rate and divided by 12. With the current 7.4% rate, a 6 lakh deposit produces 3,700 rupees per month.

Does POMIS use simple or compound interest?
POMIS uses simple interest on a fixed principal. Because the interest is paid out to you every month rather than reinvested, there is no compounding inside the scheme.

Can the POMIS interest rate change after I invest?
No. Although the government revises the rate each quarter for new accounts, the rate on your account is locked on the opening day and stays the same for the full five-year tenure.

Is TDS deducted on POMIS interest?
No, the post office does not deduct TDS on POMIS interest. However, the interest is still fully taxable at your slab rate, so you must declare it and pay the tax yourself.

How do I calculate the deposit needed for a target income?
Rearrange the formula: Principal equals desired monthly income multiplied by 12 and divided by 0.074. For 5,000 rupees a month you would need about 8.1 lakh.