CDB Regressive Income Tax Yield Calculator

CDB taxes by holding period

Two taxes hit a CDB. There's IOF, which is regressive and only bites if you redeem in the first 30 days, and there's IR, which also shrinks the longer you stay invested. The IR brackets work like this: 22.5% up to 180 days, 20% from 181 to 360, 17.5% from 361 to 720, 15% above 720 days. You get the gross amount from M = C · (1 + i)^(d/252), and the net is C + (M − C) · (1 − IR).

Say you put R$ 10,000 at 110% of CDI (effective ~16.4%) and leave it for 1 year (252 business days). The gross amount lands near R$ 11,640, a gain of R$ 1,640. At 17.5% IR (the 361-720 days bracket), the tax comes to R$ 287, which leaves you with roughly R$ 11,353, or a net gain of 13.53%. Hold past 720 days and IR drops to 15%, so you keep more of every real you earned.

Brazilian context

The regressive IR table exists on purpose. Brazil designed it to push people toward longer maturities, and that's exactly why a 24-month CDB at 110% of CDI beats a 6-month CDB at the same rate so handily. The gross is identical; the net is not. If you're parking a short-term emergency reserve, Tesouro Selic or a daily-liquidity CDB makes sense, just know the IR will be steep. For goals with a known date 12 months out or more, you want to land in the 15-17.5% bracket.

FAQ

When is IOF charged? Only when you redeem inside 30 days. It starts at 96% on day 1 and falls to 0% by day 30. Past 30 days there's no IOF at all.

What about LCI/LCA? They're IR-exempt, so net yield equals gross. An LCI at 95% of CDI works out to about the same as a CDB paying 112% of CDI once you account for IR over the same horizon.

Is IR levied only on the gain? Yes, just on the yield, never on the principal. A R$ 1,640 gain at 17.5% gives IR of R$ 287.

Worth waiting for the 15% bracket? If your liquidity allows it, yes. Holding two extra months to shave 2.5 percentage points of IR off the gain pays off well at the margin.