Cost Calculation
Quick Reference
Cost structure
Every settled charge has fees deducted before the net amount reaches your bank account. The settlement formula is:
Net Settlement = Gross Amount - MDR - Interchange - Processing Fee - FX Fee (if applicable)
Fee components
MDR (Merchant Discount Rate)
The MDR is the primary fee charged for processing a payment. It is a percentage of the transaction amount, negotiated in your merchant agreement.
| Payment Method | Typical MDR Range |
|---|---|
| Credit card (domestic) | 1.5% – 3.5% |
| Credit card (international) | 3.0% – 5.0% |
| Debit card | 0.8% – 1.5% |
| PIX | 0.0% – 1.0% |
| Boleto | R$1.50 – R$5.00 (flat) |
| SPEI | MXN $3.00 – $8.00 (flat) |
| OXXO | 2.0% – 4.0% |
These are indicative ranges. Your actual MDR depends on your contract, volume tier, and risk profile. Contact your account manager for exact rates.
Interchange fees
Interchange is the fee paid to the card-issuing bank. It varies by card brand, card type, and transaction characteristics.
| Factor | Impact on interchange |
|---|---|
| Card brand | Visa, Mastercard, Amex, Elo each have different tables |
| Card type | Premium/rewards cards have higher interchange than standard |
| Installments | Longer installment plans increase interchange |
| Domestic vs. international | Cross-border transactions have higher interchange |
| Industry | Some MCCs (Merchant Category Codes) have preferential rates |
Processing fee
A per-transaction fixed fee charged by A55 for processing the payment, regardless of the transaction amount.
| Market | Typical processing fee |
|---|---|
| Brazil | R$0.10 – R$0.50 per transaction |
| Mexico | MXN $1.00 – $3.00 per transaction |
Currency conversion (FX) fee
For cross-border transactions where the charge currency differs from the settlement currency, a foreign exchange fee is applied.
| Scenario | FX fee range |
|---|---|
| BRL → USD settlement | 1.0% – 2.5% |
| MXN → USD settlement | 1.0% – 2.5% |
| CLP → USD settlement | 1.0% – 2.5% |
| COP → USD settlement | 1.0% – 2.5% |
| Same-currency settlement | No FX fee |
All settlement fee calculations use ROUND_HALF_UP to 2 decimal places. For zero-decimal currencies (CLP, COP), the settlement amount is still computed with 2-decimal precision internally, but the final payout to your account is rounded to whole currency units.
Example calculation
A domestic credit card charge of R$1,000.00 in Brazil with standard pricing:
| Component | Rate | Amount |
|---|---|---|
| Gross amount | — | R$1,000.00 |
| MDR (2.5%) | 2.5% | -R$25.00 |
| Interchange (1.6%) | 1.6% | -R$16.00 |
| Processing fee | flat | -R$0.30 |
| Net settlement | — | R$958.70 |
A domestic PIX charge of R$500.00:
| Component | Rate | Amount |
|---|---|---|
| Gross amount | — | R$500.00 |
| MDR (0.5%) | 0.5% | -R$2.50 |
| Processing fee | flat | -R$0.10 |
| Net settlement | — | R$497.40 |
A credit card charge of MXN $2,000.00 in Mexico with USD settlement:
| Component | Rate | Amount |
|---|---|---|
| Gross amount | — | MXN $2,000.00 |
| MDR (3.0%) | 3.0% | -MXN $60.00 |
| Interchange (1.8%) | 1.8% | -MXN $36.00 |
| Processing fee | flat | -MXN $2.00 |
| Net in MXN | — | MXN $1,902.00 |
| FX fee (1.5%) | 1.5% | -MXN $28.53 |
| Net after FX | — | MXN $1,873.47 → USD equivalent |
Installment cost impact
For credit card installments, both MDR and interchange increase with the number of installments:
| Installments | MDR impact | Interchange impact |
|---|---|---|
| 1 (à vista) | Base rate | Base interchange |
| 2–6 | +0.5% – 1.0% | +0.3% – 0.8% |
| 7–12 | +1.0% – 2.0% | +0.8% – 1.5% |
How A55 calculates costs
A55 receives the interchange table from each acquirer and card scheme. When a charge settles, the exact interchange for that specific card BIN, card type, and installment plan is applied. The MDR and processing fee from your merchant agreement are added. The result is the net settlement amount visible in your settlement report and via the API.
Viewing costs via API
Each settlement record returned by the API includes the full cost breakdown:
{
"charge_uuid": "51dcca6e-7310-4b73-a94c-90835408f2ff",
"gross_amount": 1000.00,
"mdr_amount": 25.00,
"interchange_amount": 16.00,
"processing_fee": 0.30,
"fx_fee": 0.00,
"net_amount": 958.70,
"currency": "BRL",
"settled_at": "2026-02-15T14:30:00Z"
}