CDB, Savings or Treasury: Comparing the Real Return

The benchmarks: Selic, CDI and the savings-account rule

Almost all of Brazil's fixed income revolves around two rates that move in lockstep: the Selic and the CDI. The Selic is the country's base interest rate, set every 45 days by Copom, the monetary-policy committee of the Central Bank. It is the anchor from which the cost of money is built across the entire economy.

The CDI (Interbank Deposit Certificate) is the rate at which banks lend to each other overnight. In practice it runs about 0.10 percentage point below the Selic. If the Selic sits at 15% a year, the CDI hovers near 14.90%. That is why most investments are quoted as a "percentage of the CDI" rather than a fixed number: when the Selic rises or falls, the return follows on its own.

The poupança (the traditional savings account) is the exception. Since 2012 it has followed a rule fixed in law, and that rule has a trigger tied to the Selic itself:

• Selic above 8.5% a year: the savings account yields 0.5% per month + TR (a reference rate near zero) — roughly 6.17% a year.
• Selic at or below 8.5% a year: it yields 70% of the Selic + TR.

Notice the detail that changes everything: when the Selic is high, the savings account is capped near 6.17% a year and does not ride the rate up. A CDI-linked product rises right along with it. To see what the Selic and the CDI return today, run the Selic Yield Calculator and the CDI Yield Calculator.

How regressive income tax eats into the return

A CDB (bank deposit certificate), Treasury bonds and most private securities pay income tax on the earnings only (never on the principal). The rate is regressive: the longer the money stays invested, the less tax you pay. Here is the table:

The tax is withheld at source automatically on redemption — nothing to file separately. There is also the IOF, a financial-operations tax that only bites if you redeem within 30 days and falls to zero on day 30. So past one month, ignore the IOF; over the long run only the income tax matters.

The savings account: a tax exemption that rarely pays off

The big selling point of the poupança is that it is exempt from income tax for individuals. That sounds unbeatable, but the exemption is only worth something if the gross return is already decent — and with a high Selic, it isn't.

Do the math. With the Selic at 15%, the savings account yields a flat 6.17% a year. That is only about 41% of the CDI (6.17 ÷ 14.90). Any CDB paying 90% of the CDI returns 13.4% gross; even after a 15% tax bite, roughly 11.4% net is left — nearly double the tax-free savings account.

The exemption only comes close to paying off in a very specific scenario: a low Selic (below 8.5%), a very short horizon and a poor CDB. For instance, with the Selic at 8% the savings account yields 5.6% a year; a CDB at 80% of the CDI redeemed in under six months would return ~6.3% gross, and the 22.5% tax knocks that down to ~4.9% net — there the savings account wins. Outside that niche it loses. There is also the "anniversary date" quirk: you only collect the month's yield on the exact day of the deposit; withdraw one day early and you forfeit the whole month. To see this, run the Savings Simulator and put it next to a CDB with the Savings vs CDB Comparison.

CDB and what "percentage of the CDI" really means

A CDB is, in essence, a loan you make to a bank; in return it pays you interest. The most common form is the post-fixed CDB, quoted as a percentage of the CDI:

• 100% of the CDI = yields exactly the full CDI rate. With the CDI at 14.90%, that is your gross return.
• 110% of the CDI = yields 1.10 × CDI = 16.39% gross a year.
• 90% of the CDI = yields 0.90 × CDI = 13.41% gross a year.

Big banks tend to offer CDBs at 80% to 95% of the CDI; mid-size banks and digital platforms often pay 100% to 120% to attract deposits. All of them carry FGC protection (the deposit-guarantee fund): up to R$ 250,000 per taxpayer per institution, capped at R$ 1 million every four years. So comparing two CDBs comes down to comparing their percentage of the CDI and the time to maturity. The CDB Multi-Scenario Calculator projects several percentages and terms at once, already net of tax.

There is also Tesouro Selic, a government bond that yields essentially the Selic and carries the lowest credit risk in the country (the government itself). It has no FGC, but it is considered Brazil's safest asset. The trade-off is the B3 custody fee of 0.20% a year — though the first R$ 10,000 invested in Tesouro Selic is exempt from that fee.

A real-world comparison, with numbers

Let's line up R$ 10,000 invested for 2 years (730 days, so the income tax drops to the lowest 15% bracket). For the example, assume a Selic of 15% a year, a CDI of 14.90% and a TR near zero — illustrative figures, since these rates change.

Even after losing 15% to tax, the CDB at 100% of the CDI earns R$ 2,722 versus R$ 1,272 from the tax-free savings account — more than double. Tesouro Selic ties the 100%-CDI CDB: it earns a touch more gross (it tracks the full Selic), but the custody fee gives that small edge back. And the 110%-CDI CDB pulls ahead of all of them. To build your own grid with the rates and term you actually have, use the 4-Way Investment Comparison.

Frequently asked questions

CDB or Tesouro Selic for an emergency fund?

Both work, as long as they offer daily liquidity. Tesouro Selic is the safest (government-backed) and barely fluctuates in the short term. A daily-liquidity CDB at 100% of the CDI or more, from an FGC-covered bank, is equally valid and sometimes yields a bit more. For a reserve, avoid bonds with a long maturity and no early redemption.

What does "100% of the CDI" mean exactly?

It means the security pays the full CDI rate for the period. If the CDI accrued 14.90% over the year, a CDB at 100% of the CDI returns that 14.90% gross. Above 100% you earn a premium; below it, a fraction. The CDI Yield Calculator turns any percentage into a money figure.

Is it worth leaving money in the savings account?

Almost never, while the Selic is high. The savings account is stuck near 6.17% a year, while CDI-linked securities clear 14% gross. The tax exemption does not cover that gap. The poupança only makes sense as a very short-term parking spot or for someone with no access to another product.

Is the tax charged every month or only on redemption?

On a CDB and on Treasury bonds, income tax is withheld only on redemption or at maturity, on the accumulated profit. There is no "come-cotas" in these products — that semi-annual levy applies to certain investment funds, not to individual bonds. So your money compounds on the full balance while it stays invested.

Are LCI and LCA better because they are tax-exempt?

They are exempt from income tax for individuals, so the fair comparison is always on the net return. An LCI at 90% of the CDI can match a CDB at 105% to 110% of the CDI after tax. The weak spot is usually the lock-up period (no early redemption), which makes them a poor fit for an emergency fund.