CDI: What It Is and Why It Affects Your Investments
Have you ever seen a financial application advertised as “yields 100% of the CDI” and were unsure what that meant exactly? Or perhaps you heard that the CDI rate went up or down and didn’t know why it matters to the money you have saved? If any of these situations sound familiar, this article was made for you.
The CDI is one of the most cited indicators in the Brazilian financial market — and also one of the most misunderstood by the average investor. It appears in CDBs, investment funds, LCIs, LCAs, debentures and even in comparisons with savings accounts. Understanding it is not a luxury reserved for specialists: it is a basic skill for anyone who wants to make more informed financial decisions.
In the next sections, you will understand what CDI is, how it is calculated, why it directly influences your returns, and how to use it as a reference when evaluating fixed-income investments. Let’s start from the beginning.
What is CDI?
CDI is the acronym for Interbank Certificate of Deposit. It is a very short-term title — usually one business day — that banks issue to each other to meet a requirement of the Brazilian financial system: to close the cash on a positive balance at the end of each day.
When a bank ends the day with more money going out than coming in, it needs to raise funds quickly. Another bank, which has a positive balance, can lend that money. This operation is done through CDIs. The CDI rate is, therefore, the average interest rate charged in these operations between financial institutions.
Although you, as an individual, cannot buy a CDI directly, this rate serves as a reference (benchmark) for a huge amount of investment products available to the public. When a bank says that its CDB yields “110% of the CDI”, it means that the product’s profitability is calculated as 110% of the accumulated CDI rate over the period.
How the CDI rate is calculated and where to check it
The CDI rate is calculated daily by B3 (the Brazilian stock exchange, which also manages the clearing house for private securities). The calculation considers the average of the rates charged in interbank operations recorded on each business day.
In practice, the daily CDI rate is very close to the Selic rate — the basic interest rate of the Brazilian economy, defined by the Monetary Policy Committee (Copom) of the Central Bank. The difference between the two is usually small (generally tenths of a percentage point), but they are not identical.
> Where to check the current CDI value: Since the CDI rate changes according to Copom decisions and market conditions, it is important to verify the updated value directly from the official source. You can check the CDI rate on the B3 website (b3.com.br) or the Central Bank of Brazil (bcb.gov.br). Never trust values cited in articles or videos without verifying if they are still current.
Why does CDI affect your investments?
The relationship between CDI and your investments is direct: most fixed-income products in Brazil have their profitability linked to CDI. This means that when the CDI rate rises, these investments tend to yield more; when it falls, they yield less.
See the main types of investments indexed to CDI:
- CDB (Certificate of Bank Deposit): issued by banks, often offered as a percentage of CDI (e.g., 90%, 100%, 110% of CDI).
- LCI and LCA (Real Estate and Agribusiness Credit Letters): are also typically indexed to CDI and are exempt from Income Tax for individuals.
- DI Funds: investment funds that seek to track CDI, investing primarily in short-term public and private securities.
- Debentures and CRIs/CRAs: some of these papers also use CDI as a remuneration reference.
Even investments that are not directly indexed to CDI, such as Treasury Selic (which follows the Selic rate), are indirectly influenced, since Selic and CDI move very closely together. To better understand the differences between fixed-income options, it is worth checking this comparison: CDB vs Treasury Direct: Which Yields More in 2026?
CDI vs. savings account: why the comparison matters
The savings account is the most popular investment among Brazilians, largely due to simplicity and the guarantee of the FGC (Credit Guarantor Fund). However, it has a different remuneration rule than products linked to CDI.
Savings account profitability follows a rule set by the Central Bank:
- When Selic is above 8.5% per year, the savings account yields 0.5% per month + Reference Rate (TR).
- When Selic is equal to or below 8.5% per year, the savings account yields 70% of Selic + TR.
> Attention: the TR varies and may be zero or close to zero in some periods. Always check current conditions on the Central Bank website (bcb.gov.br) before making any decision.
In many scenarios of higher interest rates, products that yield 100% of CDI or more tend to outperform savings accounts in terms of gross profitability. However, you need to consider taxation — which brings us to the next point. If you want to better understand savings account profitability in practice, see: How much does R$ 1,000 yield in a savings account per month?
Taxation of investments linked to CDI
A crucial point that many investors ignore: gross returns are not what you receive. On products like CDBs and DI funds, Income Tax (IR) is charged, withheld at the source, with regressive rates according to the application period:
| Application period | IR Rate |
|---|---|
| Up to 180 days | 22.5% |
| From 181 to 360 days | 20% |
| From 361 to 720 days | 17.5% |
| Over 720 days | 15% |
In addition to IR, some investment funds charge the so-called come-cotas: a semiannual advance on IR, which applies to earnings accumulated in May and November of each year.
LCIs and LCAs are already exempt from IR for individuals, which can make them more attractive depending on the percentage of CDI they offer. To compare correctly, always calculate the net profitability (after taxes and fees), not just the gross profitability announced.
> Attention: tax rules can be changed by law. Always consult current legislation or a specialized professional before investing.
How to use CDI to evaluate investments: a practical guide
Knowing that a product yields “X% of CDI” is useful, but it only makes sense when you understand how to turn it into a real evaluation. Follow this reasoning:
- Find out the current CDI rate. Access the B3 or Central Bank website and note the current annualized CDI rate.
- Calculate the estimated gross profitability. If a CDB yields 110% of CDI and CDI is at a certain percentage per year, multiply the two values to get the approximate gross profitability.
- Deduct Income Tax. Use the regressive table above to estimate how much IR will be charged, depending on the period you intend to keep the investment.
- Compare with other options. An LCI at 90% of CDI exempt from IR can yield more than a CDB at 100% of CDI with IR, depending on the period and applicable rate.
- Consider the risk of the issuer. CDBs from smaller banks usually offer higher percentages precisely because credit risk is greater. The FGC guarantees up to R$ 250,000 per CPF per institution (check current limits at fgc.org.br), but it is important to know this limitation.
- Check costs and fees. DI funds charge annual management fees, which erode profitability. Always compare net returns after fees and taxes.
Advantages and risks of CDI-linked investments
As with any financial product, there are positive and negative points to consider. Every investment involves risk, and this is no different for assets indexed to CDI.
Advantages:
- Predictable profitability linked to a reliable and transparent indicator.
- Diversity of available products (CDBs, LCIs, LCAs, DI funds).
- Good liquidity in many cases, especially in CDBs with daily liquidity.
- Protection by FGC in some products, within current limits.
Risks and disadvantages:
- Credit risk: the issuer (bank or company) may face financial difficulties.
- Liquidity risk: some CDBs do not allow withdrawal before maturity.
- CDI variation risk: if the rate falls, the return falls with it — there is no guarantee of fixed future profitability.
- Tax cost: the incidence of IR reduces net profitability, especially in short periods.
- Inflation: if CDI stays below inflation for a prolonged period, the real purchasing power of the investment may decline.
Conclusion: use CDI as a compass, not a destination
CDI is a powerful reference tool for the Brazilian investor. Understanding how it works allows you to compare products more clearly, question advertised profitability, and make more informed decisions — without falling into traps of superficial comparisons.
Remember: a product that yields more is not necessarily better if it comes with more risk, less liquidity, or a higher tax cost. CDI is the starting point of the analysis, not the end of it. Whenever you are about to evaluate an investment, check the current rate in official sources, calculate the net profitability, and consider your profile, your goals, and your timeframe.
To further expand your knowledge about investments beyond traditional fixed income, it is worth reading Invest beyond savings: options that yield more.
> Important note: This article is exclusively educational and informational in nature. It does not constitute investment recommendation, financial consulting, or indication of any specific product. Past profitability does not guarantee future results, and every investment involves risks. For investment decisions appropriate to your profile and financial situation, consult a certified professional or investment advisor duly registered with the CVM (Brazilian Securities Commission).
