SAC vs Price amortization in Brazil

What the sources say

The BCB’s Resolução CMN 4.676 names SAC and SACRE (a related system with increasing amortization) in article 6, but does not define them. The only central-bank text Payotte found that describes them is Technical Note 56 of October 2025. Its authors write that its opinions do not necessarily reflect the BCB’s views, so treat it as a description, not a rule. It says Price was designed to keep the nominal instalment constant, with most of the early instalments going to interest, and that under SAC the instalment is the sum of an interest part, tied to the outstanding balance, and a fixed amortization part, so it decreases. It adds that SAC is currently the most used system in Brazil.

The formulas

Let P be the amount borrowed, n the number of months and i the monthly rate.

• Price: instalment M = P × i / (1 − (1 + i)^−n). Interest in month k = i × balance; the rest of M repays principal.
• SAC: amortization A = P / n every month. Instalment k = P/n + i × balance before k, where the balance before k is P − (k − 1) × A. The first instalment is P/n + P × i; the last is A × (1 + i).

Two practical points. First, the monthly rate is derived from the annual one: i = (1 + annual rate)^(1/12) − 1, not annual rate ÷ 12. Second, these are the bare schedules. Many contracts add the monthly administration fee, insurance premiums and, where the contract provides it, an inflation or savings-account adjustment of the balance, which change each instalment (mortgage insurance, CET).

Worked calculation

The BCB’s series 20774 gives 11.28% a year for August 2026 (all new housing loans to individuals). Converted: (1 + 0.1128)^(1/12) − 1 = 0.8946% a month. This is a calculation at a statistic, not a rate any lender offers. Loan R$ 500,000, 360 months:

Reading it: SAC costs about R$ 1,200 more per month at the start, but its instalment falls steadily and the total interest is lower, because principal is repaid faster. Price is easier on a tight starting budget, and in its first year it repays only about R$ 2,400 of principal out of R$ 500,000 in this example. The same property with the same rate costs about R$ 371,000 less over the full term under SAC. These figures ignore insurance, fees and any balance adjustment, and they assume the full term runs; early repayment changes both.

Why it matters for the loan size

Under article 6 of Resolução 4.676 the ceiling is 80% of the appraisal for a residential purchase, but “poderá ser de até 90%” when SAC or SACRE is used. A buyer who needs the extra 10% therefore has a regulatory reason to choose SAC, with a larger first instalment. Because the lender also tests repayment capacity on the highest instalment in the contract, a high SAC first instalment can reduce what you qualify for. That test is the lender’s own (see how mortgages work).

Which to choose

There is no legal answer. A question to ask yourself: can the household carry the first SAC instalment, and does it expect to repay early or sell? Comparing the CET of the two offers, rather than the rate alone, is the safer test. Try figures in the mortgage calculator.

Which professional to consult

A mortgage lender can produce the full schedule with insurance and fees for each system (mortgage lender). A lawyer registered with the OAB can explain contract clauses on balance adjustment and early repayment (property lawyer).