Updated July 27, 2026
In this guide
Wrong inputs
| Problematic input | Verifiable input |
|---|---|
| “12” monthly because the ad says 12% p.a. | 12% annual with nominal/effective type confirmed |
| Property price | Amount actually financed |
| Zero adjustment without reading the index clause | Contractual TR or series |
| Financial payment as total payment | Add insurance and fees |
| Contribution without a goal | Explicit term or payment reduction |
Nominal and effective rates
12% effective p.a. ≠ 1% monthly
Hypothetical 12% annual rates used only to demonstrate nominal and effective conversion.
Parameters used
- Financed amount
- R$300,000.00
- Term
- 360 months
- Interest rate
- 12.00% effective per year
- System
- SAC
- Monthly adjustment
- —
- Extra amortization
- —
Calculated results
| Scenario | 12% effective yearly | 12% nominal yearly |
|---|---|---|
| First payment | R$3,679.97 | R$3,833.33 |
| Last payment | R$842.45 | R$842.88 |
| Total interest | R$513,820.18 | R$541,502.15 |
| Total paid | R$813,820.18 | R$841,502.15 |
| Effective term | 360 months | 360 months |
| Accumulated adjustment | R$0.00 | R$0.00 |
Selected installments
| Payment no. | Payment | Interest | Amortization | Closing balance |
|---|---|---|---|---|
| 1 | R$3,679.97 | R$2,846.64 | R$833.33 | R$299,166.67 |
| 12 | R$3,592.99 | R$2,759.66 | R$833.33 | R$290,000.04 |
| 60 | R$3,213.44 | R$2,380.11 | R$833.33 | R$250,000.20 |
| 180 | R$2,264.56 | R$1,431.23 | R$833.33 | R$150,000.60 |
| 360 | R$842.45 | R$7.92 | R$834.53 | R$0.00 |
Checklist before relying
Confirm principal, remaining term, period and rate type, system, adjustment, first due date, costs and each amortization goal. Keep the data reference and compare the first lines with the statement.
Treat every result as an estimate. Record an unknown input as an assumption instead of a fact.
What may differ in a contract
- Proposal labels may not match field labels; use the calculation worksheet, not only the advertisement.
- Current balance and remaining term are better inputs for an active contract than original values.
Limits of this analysis
- The checklist reduces input errors but does not validate a contract or provide financial advice.
- Results remain subject to the modelled system, dates and costs.
Sources and review
- Central Bank of Brazil — Citizen Calculator · July 27, 2026
- Central Bank of Brazil — TR series SGS 226 · July 27, 2026