See how an initial investment plus monthly contributions grows with compound interest, and how much income tax takes at the end.
Compound interest means the interest earned in one period earns interest in the next. Over long periods this compounding is the dominant force — more important than the rate itself. An investment of R$ 10,000 at 1% per month reaches R$ 33,003 in 10 years with no contributions; add R$ 500 a month and the result is R$ 148,756. The monthly contribution matters as much as the starting capital, especially in the early years.
The income tax on most Brazilian fixed-income investments follows a regressive table: 22.5% for up to 180 days, 20% for 181-360, 17.5% for 361-720, and 15% above 720 days. The tax is levied on the interest only, not on the principal. This simulator applies the rate corresponding to the total holding period, which is how a single CDB or a Tesouro Direto bond works. It does not model come-cotas (the semi-annual tax anticipation of funds) or the IOF that applies in the first 30 days.
This is a simplified model. Real investments have daily instead of monthly compounding, variable rates, fees, and products with specific tax treatment (LCI/LCA are tax-exempt, for example). The simulator gives you the order of magnitude and the effect of time and contributions — use it to build intuition, then check the specific product.
Balance after n months = PV × (1+i)^n + PMT × [(1+i)^n − 1] / i. Income tax = (balance − total contributions) × regressive rate. Net = balance − tax.
Depends on the product. A CDB at 100% of CDI is about 0.85% monthly in the current environment; at 120% of CDI about 1.02%. Tesouro Selic is close to 100% of CDI. The poupança is about 0.5% monthly. Use the net-of-fee rate your institution quotes.
In most fixed-income products, yes — the bank withholds the tax when you redeem or when the bond matures. The simulator shows the tax so you can see the difference between gross and net.
No. The balance is nominal. To estimate real (inflation-adjusted) return, subtract the expected monthly inflation from the rate before simulating.
They are tax-exempt for individuals. Set the tax to zero mentally — the gross balance in the simulator is your net balance.
No. The calculation runs entirely in JavaScript on your device.
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