Financing guide

Why a lender's payment may differ from the simulator

Reconcile rates, dates, insurance, fees, indexation and rounding when a contract payment does not match an estimate.

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Updated August 31, 2026

In this guide
  1. Diagnostic sequence
  2. Numerical reconciliation
  3. What to check

Diagnostic sequence

Start with inputs: financed amount, remaining term, system, rate, annual type, first due date and index. Then separate the financial payment from costs.

difference = adjustment + insurance + fees + dates + rounding

Numerical reconciliation

This example keeps debt and interest unchanged and adds BRL 150 monthly. The payment grows, while that cost does not change interest, amortization or balance.

BCB reference rate for fixed-rate real-estate financing: 2026-07, median of 3 institutions.

Parameters used

Financed amount
R$300,000.00
Term
360 months
Interest rate
14.9797% effective per year
System
SAC
Monthly adjustment
—
Extra amortization
—

Calculated results

ScenarioWithout monthly costWith BRL 150 monthly
First paymentR$4,343.33R$4,493.33
Last paymentR$844.29R$994.29
Total interestR$633,557.33R$633,557.33
Total paidR$933,557.33R$987,557.33
Effective term360 months360 months
Accumulated adjustmentR$0.00R$0.00

Selected installments

Payment no.PaymentInterestAmortizationClosing balance
1R$4,493.33R$3,510.00R$833.33R$299,166.67
12R$4,386.08R$3,402.75R$833.33R$290,000.04
60R$3,918.08R$2,934.75R$833.33R$250,000.20
180R$2,748.09R$1,764.76R$833.33R$150,000.60
360R$994.29R$9.76R$834.53R$0.00
Outstanding balance over timeWithout monthly cost / With BRL 150 monthly
Outstanding balance over timeWithout monthly costWith BRL 150 monthly
Open in simulator

What to check

Line Question
Interest Do rate and period match?
Adjustment Which observation and date were used?
Amortization Do system and opening balance match?
Costs Are MIP, DFI or fees present?

If the sum still fails to reconcile, request the lender's calculation worksheet. A difference alone does not prove that either side is wrong.

What may differ in a contract

  • MIP, DFI, administration fees and other charges may vary with age, balance, property and month.
  • An irregular first due date and day-count conventions may create proportional interest.

Limits of this analysis

  • The example does not reproduce a lender's internal methodology.
  • It excludes arrears, litigation, construction grace periods and contract amendments.

Sources and review