> For the complete documentation index, see [llms.txt](https://docs.fonbnk.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fonbnk.com/server-to-server/integration-guide/flow-examples/crypto-to-fiat.md).

# Crypto to Fiat

A POLYGON\_USDT (crypto) deposit paying out NGN (fiat) — the classic off-ramp.

{% hint style="info" %}
Every response on this page is a **sandbox** capture, so the contract address, the bank list and the rates are sandbox values. Production addresses are on [Supported countries and cryptocurrencies](/supported-countries-and-cryptocurrencies.md); read yours from [Get available currencies](/server-to-server/api-endpoints/get-available-currencies.md) rather than either.
{% endhint %}

{% stepper %}
{% step %}

#### Call [Get available currencies](/server-to-server/api-endpoints/get-available-currencies.md)

{% code title="Example response (trimmed to the two entries we need)" overflow="wrap" expandable="true" %}

```json
[
  {
    "currencyType": "crypto",
    "currencyCode": "POLYGON_USDT",
    "paymentChannels": [
      {
        "name": "Crypto",
        "type": "crypto",
        "transferTypes": ["manual"],
        "isDepositAllowed": true,
        "isPayoutAllowed": true
      }
    ],
    "currencyDetails": {
      "network": "POLYGON",
      "asset": "USDT",
      "contractAddress": "0x3b3a06b48119c035a2e86afdb69d9ad930643b3d"
    },
    "pairs": ["fiat", "merchant_balance"]
  },
  {
    "currencyType": "fiat",
    "currencyCode": "NGN",
    "paymentChannels": [
      {
        "name": "Bank transfer",
        "type": "bank",
        "transferTypes": ["manual"],
        "isDepositAllowed": true,
        "isPayoutAllowed": true
      },
      {
        "name": "Airtime",
        "type": "airtime",
        "transferTypes": [],
        "isDepositAllowed": false,
        "isPayoutAllowed": true,
        "carriers": [
          { "code": "ng_mtn", "name": "MTN Nigeria" },
          { "code": "ng_airtel", "name": "Airtel Nigeria" },
          { "code": "ng_glo", "name": "Glo Mobile Nigeria" },
          { "code": "ng_9mobile", "name": "9Mobile Nigeria" }
        ]
      }
    ],
    "currencyDetails": { "countryIsoCode": "NG" },
    "pairs": ["crypto", "merchant_balance"]
  }
]
```

{% endcode %}

POLYGON\_USDT allows deposits, and NGN's `bank` channel has `isPayoutAllowed: true`. So POLYGON\_USDT → NGN over `bank` is legal. `airtime` would work as a payout too — add a `carrierCode` if you use it.
{% endstep %}

{% step %}

#### Call [Get order limits](/server-to-server/api-endpoints/get-order-limits.md)

* depositPaymentChannel: "<mark style="color:yellow;">crypto</mark>"
* depositCurrencyType: "<mark style="color:yellow;">crypto</mark>"
* depositCurrencyCode: "<mark style="color:yellow;">POLYGON\_USDT</mark>"
* payoutPaymentChannel: "<mark style="color:yellow;">bank</mark>"
* payoutCurrencyType: "<mark style="color:yellow;">fiat</mark>"
* payoutCurrencyCode: "<mark style="color:yellow;">NGN</mark>"
* payoutCountryIsoCode: "<mark style="color:yellow;">NG</mark>"

{% code title="Example response" overflow="wrap" %}

```json
{
    "deposit": {
        "min": 1,
        "max": 500,
        "minUsd": 1,
        "maxUsd": 500,
        "step": 0.000001,
        "supportsDecimals": true
    },
    "payout": {
        "min": 1409,
        "max": 704460,
        "minUsd": 1,
        "maxUsd": 500,
        "step": 1,
        "supportsDecimals": false
    }
}
```

{% endcode %}

The user can send 1 to 500 POLYGON\_USDT and receive 1,409 to 704,460 NGN. Note that the NGN leg is whole units only — `supportsDecimals: false`, `step: 1`.

The user wants 30,000 NGN. Check their KYC tier with the [KYC flow](/server-to-server/kyc-flow.md), passing the amounts. Off-ramp KYC is a per-country switch and South Africa is currently the only country where it is on, so a Nigerian off-ramp needs none — but read `offrampKycRequired` rather than assuming. See [KYC](/kyc.md).
{% endstep %}

{% step %}

#### Call [Create quote](/server-to-server/api-endpoints/create-quote.md)

The amount goes on the payout leg, because the user asked for an NGN figure.

{% code title="Example request" %}

```json
{
    "deposit": {
        "paymentChannel": "crypto",
        "currencyType": "crypto",
        "currencyCode": "POLYGON_USDT"
    },
    "payout": {
        "paymentChannel": "bank",
        "currencyType": "fiat",
        "currencyCode": "NGN",
        "countryIsoCode": "NG",
        "amount": 30000
    }
}
```

{% endcode %}

{% code title="Example response" overflow="wrap" expandable="true" %}

```json
{
    "quoteId": "692d9874a60e2135463730cf",
    "quoteExpiresAt": "2025-12-01T14:00:28.208Z",
    "deposit": {
        "paymentChannel": "crypto",
        "currencyType": "crypto",
        "currencyCode": "POLYGON_USDT",
        "currencyDetails": {
            "network": "POLYGON",
            "asset": "USDT",
            "contractAddress": "0x3b3a06b48119c035a2e86afdb69d9ad930643b3d"
        },
        "cashout": {
            "amountBeforeFees": 21.272315,
            "amountAfterFees": 21.272315,
            "amountBeforeFeesUsd": 21.272315,
            "amountAfterFeesUsd": 21.272315,
            "chargedFees": [],
            "chargedFeesUsd": [],
            "totalChargedFees": 0,
            "totalChargedFeesUsd": 0,
            "exchangeRate": 1,
            "exchangeRateAfterFees": 1,
            "chargedFeesPerRecipient": {},
            "chargedFeesPerRecipientUsd": {},
            "feeSettings": []
        },
        "fieldsToCreateOrder": [
            {
                "key": "blockchainWalletAddress",
                "type": "string",
                "label": "Your wallet address",
                "required": false
            },
            {
                "key": "depositSandboxForcedFlow",
                "type": "enum",
                "label": "Sandbox deposit forced flow",
                "required": false,
                "defaultValue": "deposit_success",
                "options": [
                    { "label": "Deposit success", "value": "deposit_success" },
                    { "label": "Deposit invalid", "value": "deposit_invalid" }
                ]
            }
        ],
        "transferType": "manual"
    },
    "payout": {
        "paymentChannel": "bank",
        "currencyType": "fiat",
        "currencyCode": "NGN",
        "currencyDetails": { "countryIsoCode": "NG" },
        "cashout": {
            "amountBeforeFees": 31088,
            "amountAfterFees": 30000,
            "amountBeforeFeesUsd": 21.272315,
            "amountAfterFeesUsd": 20.527839,
            "chargedFees": [
                { "id": "service_fee", "type": "percentage", "recipient": "platform", "amount": 777.2 },
                { "id": "merchant_fee", "type": "percentage", "recipient": "merchant", "amount": 310.88 }
            ],
            "chargedFeesUsd": [
                { "id": "service_fee", "type": "percentage", "recipient": "platform", "amount": 0.531808 },
                { "id": "merchant_fee", "type": "percentage", "recipient": "merchant", "amount": 0.212723 }
            ],
            "totalChargedFees": 1088.08,
            "totalChargedFeesUsd": 0.744531,
            "exchangeRate": 1461.43,
            "exchangeRateAfterFees": 1514.4312,
            "chargedFeesPerRecipient": { "platform": 777.2, "merchant": 310.88 },
            "chargedFeesPerRecipientUsd": { "platform": 0.531808, "merchant": 0.212723 },
            "feeSettings": [
                { "id": "service_fee", "recipient": "platform", "type": "percentage", "value": 2.5, "min": 0, "max": "Infinity" },
                { "id": "merchant_fee", "recipient": "merchant", "type": "percentage", "value": 1, "min": 0, "max": "Infinity" }
            ]
        },
        "fieldsToCreateOrder": [
            { "key": "phoneNumber", "label": "Phone Number", "required": true, "type": "phone" },
            {
                "key": "bankCode",
                "label": "Bank name",
                "required": true,
                "type": "enum",
                "options": [
                    { "label": "Sandbox Bank", "value": "1" },
                    { "label": "Sandbox Bank 2", "value": "2" },
                    { "label": "Sandbox Bank 3", "value": "3" }
                ]
            },
            { "key": "bankAccountNumber", "label": "Bank Account Number", "required": true, "type": "string" },
            {
                "key": "payoutSandboxForcedFlow",
                "type": "enum",
                "label": "Sandbox payout forced flow",
                "required": false,
                "defaultValue": "payout_success",
                "options": [
                    { "label": "Payout success", "value": "payout_success" },
                    { "label": "Payout failed", "value": "payout_failed" }
                ]
            }
        ]
    }
}
```

{% endcode %}

To receive 30,000 NGN the user must deposit **21.272315** POLYGON\_USDT — that is `deposit.cashout.amountBeforeFees`. Collect the fields marked `required` on both legs:

* `phoneNumber`
* `bankCode` (from the enum options)
* `bankAccountNumber`

{% hint style="info" %}
`blockchainWalletAddress` is **not** required on a crypto *deposit* leg — it is `required: false` there, and `required: true` only when crypto is the payout. Send it anyway if you know it: it comes back in the transfer details as `senderWalletAddress`, which is what the user sees as "your wallet address". It is a display value, not a filter — the deposit is recognised from the transaction hash you confirm with.
{% endhint %}
{% endstep %}

{% step %}

#### Call [Create order](/server-to-server/api-endpoints/create-order.md)

{% code title="Example request" overflow="wrap" expandable="true" %}

```json
{
    "quoteId": "692d9874a60e2135463730cf",
    "userCountryIsoCode": "NG",
    "userEmail": "someuser@example.com",
    "userIp": "223.134.123.12",
    "deposit": {
        "paymentChannel": "crypto",
        "currencyType": "crypto",
        "currencyCode": "POLYGON_USDT"
    },
    "payout": {
        "paymentChannel": "bank",
        "currencyType": "fiat",
        "currencyCode": "NGN",
        "countryIsoCode": "NG",
        "amount": 30000
    },
    "fieldsToCreateOrder": {
        "blockchainWalletAddress": "0x5b7ae3c6c87f4a3f94b35c77233b13191ebfad20",
        "phoneNumber": "2348012345678",
        "bankCode": "1",
        "bankAccountNumber": "1234567890"
    }
}
```

{% endcode %}

{% code title="Example response (transfer instructions excerpt)" overflow="wrap" expandable="true" %}

```json
{
    "quoteUsed": true,
    "order": {
        "_id": "692d98b0a60e21354637311a",
        "countryIsoCode": "NG",
        "userId": "686671f07730d8d1a9b2260a",
        "userEmail": "someuser@example.com",
        "status": "deposit_awaiting",
        "deposit": {
            "paymentChannel": "crypto",
            "currencyType": "crypto",
            "currencyCode": "POLYGON_USDT",
            "currencyDetails": {
                "network": "POLYGON",
                "asset": "USDT",
                "contractAddress": "0x3b3a06b48119c035a2e86afdb69d9ad930643b3d"
            },
            "providedFieldsToCreateOrder": {
                "blockchainWalletAddress": "0x5b7ae3c6c87f4a3f94b35c77233b13191ebfad20"
            },
            "transferInstructions": {
                "type": "manual",
                "instructionsText": "Please send the exact amount of crypto to the address below. Make sure to send only USDT on the Polygon network. Sending any other assets or using a different network may result in loss of funds.",
                "transferDetails": [
                    { "id": "recipientWalletAddress", "label": "Wallet address to send", "value": "0xdc9cbad0c43f912a66cd44cd22a15c04368e659f" },
                    { "id": "senderWalletAddress", "label": "Your wallet address", "value": "0x5b7ae3c6c87f4a3f94b35c77233b13191ebfad20" },
                    { "id": "amountToSend", "label": "Amount to send", "value": "21.272315" },
                    { "id": "cryptoTransactionRequestAdditionalData", "label": "Crypto transaction additional data", "value": "" }
                ],
                "fieldsToConfirmOrder": [
                    { "key": "blockchainTransactionHash", "type": "string", "label": "Transaction hash", "required": true }
                ]
            }
        },
        "payout": {
            "paymentChannel": "bank",
            "currencyType": "fiat",
            "currencyCode": "NGN",
            "currencyDetails": { "countryIsoCode": "NG" },
            "providedFieldsToCreateOrder": {
                "phoneNumber": "2348012345678",
                "bankCode": "1",
                "bankAccountNumber": "1234567890"
            }
        },
        "statusChangeLogs": [],
        "createdAt": "2025-12-01T13:31:28.372Z",
        "updatedAt": "2025-12-01T13:31:28.372Z",
        "expiresAt": "2025-12-01T14:01:28.156Z"
    }
}
```

{% endcode %}

From `transferInstructions` and `fieldsToConfirmOrder` we know:

* The user sends <mark style="color:yellow;">21.272315</mark> Polygon USDT to <mark style="color:yellow;">0xdc9cbad0c43f912a66cd44cd22a15c04368e659f</mark>. Send the exact amount, on that network, to that address.
* `senderWalletAddress` echoes the wallet address you passed, for the user to check against their own wallet.
* Confirming the order needs <mark style="color:yellow;">blockchainTransactionHash</mark>.
  {% endstep %}

{% step %}

#### The user sends the exact amount to that address

{% endstep %}

{% step %}

#### Call [Confirm order](/server-to-server/api-endpoints/confirm-order.md) with the transaction hash

{% code title="Example request" %}

```json
{
  "orderId": "692d98b0a60e21354637311a",
  "fieldsToConfirmOrder": {
     "blockchainTransactionHash": "0xe168c39bf7165c0eaa88e4df1e21e987666e44f11f2bea6f9be1c145f382dade"
  }
}
```

{% endcode %}
{% endstep %}

{% step %}

#### We confirm the transaction on-chain and send the NGN payout

{% endstep %}

{% step %}

#### Wait for "<mark style="color:yellow;">payout\_successful</mark>"

Handle the `order-status-change` [webhook](/server-to-server/webhooks.md), or poll [Get order](/server-to-server/api-endpoints/get-order.md).
{% endstep %}
{% endstepper %}


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