First the cycle, then the product
Treasury starts with a simple calculation: how much comes in, when it comes in, how much goes out, when it goes out. That is the operating cycle: the time between paying the supplier and being paid by the customer. Seasonality, average collection period, payroll, taxes, loan installments. Only after drawing up that calendar does it make sense to talk about where to invest. Whoever chooses the product before knowing their own cycle is deciding blind.
Every real with a date: cash matched to payments
Matching liquidity means splitting the cash into layers and giving each one a redemption period compatible with the date on which that money will be used. The day-to-day layer needs to be available the same day or the next day (the market calls this D+0 and D+1) and cannot fluctuate. The layer for known commitments (the quarter's tax, the 13th-month salary, a construction project) can go into a security that matures on that date. The structural surplus, the part with no planned use, is the only one that accepts a longer term. Very short-term investments have details that bite: in fixed income there is a regressive IOF (a federal tax on financial operations) on the earnings in the first 30 days, and income tax (IR) follows a regressive table by holding period (22.5% up to 180 days, falling to 15% above 720 days). Redeeming too early is not just giving up earnings: it is paying tax at the worse rate.
What maturity and price fluctuation do to cash
A fixed-income security with a maturity date has a price that fluctuates until then. If you buy a fixed-rate or an IPCA+ bond (one that pays inflation plus a fixed rate) and need to sell before maturity, you sell at the day's price: it may be above or below what you expected. This is called mark-to-market, and it is exactly the mechanism that turns a "conservative" investment into a problem when cash gets tight. It is also worth knowing the protections and their limits: CDBs (bank certificates of deposit) and some other securities are covered by the FGC (Brazil's deposit guarantee fund), which applies to companies (CNPJ, the company tax ID) and is limited to R$ 250,000 per institution, with an overall cap of R$ 1 million every four years per holder. A company with significant cash blows through that limit quickly. From there the conversation becomes about issuer risk and diversification, not about a guarantee.
A company's treasury is not personal investing
They are different objectives. The company's cash exists to sustain the operation and cannot be held hostage to price swings; it already carries the business's risk. The owner's personal wealth has another horizon, another tolerance and another legal owner. Mixing the two creates three unwanted effects: investment decisions contaminated by operational need, family money exposed to the company's risk, and an accounting mess that nobody wants to explain later. Taxation also follows its own rules for a company and varies by regime (Simples, Presumido or Real, the three Brazilian corporate tax regimes), so that part is decided together with your accountant, not by estimate. Structuring begins by drawing the line: what is operating cash, what is the company's strategic reserve and what is already personal wealth that has been distributed.