# Create Refund

> Refund a paid or overpaid invoice in full or for the overpayment difference back to the first confirmed sender address.

`POST /v1/refunds`

:::endpoint
POST /v1/refunds
:::

**API key:** `Payment`

Creates an on-chain refund for a `paid` or `paid_over` invoice within 14 days of its last confirmed deposit. Both the destination address and the refund amount are computed automatically by the server: funds return to the sender address of the first confirmed invoice deposit (`first_sender`), and the merchant balance is debited for `amount + fee`.

## Request body

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `invoice_id` | string | Yes | Prefixed invoice identifier (`inv_...`) belonging to a project in the key's scope |
| `mode` | string | Yes | `"full"` (returns the remaining refundable invoice balance) or `"overpayment"` (returns only the excess over the requested invoice amount) |
| `external_order_id` | string | Yes | Your idempotency reference (max 200 characters), unique per merchant and environment |

## Example request

```json
{
  "invoice_id": "inv_7K2M9P4Q8R1X5Z3A0bC2dE",
  "mode": "full",
  "external_order_id": "refund-1042-full"
}
```

## Code examples

Each tab uses an official SDK with a Payment key (`pk_`). Signing, serialization, safe retries, and typed errors are handled by the SDK.

```curl
API_KEY_ID="pk_live_xxxxxxxxxxxx"
API_SECRET="sk_live_xxxxxxxxxxxx"
BODY='{"invoice_id":"inv_7K2M9P4Q8R1X5Z3A0bC2dE","mode":"full","external_order_id":"refund-1042-full"}'

TS=$(date +%s)
BODY_HASH=$(printf '%s' "$BODY" | openssl dgst -sha256 -hex | sed 's/^.* //')
SIGNATURE=$(printf '%s\n%s\n%s\n%s\n%s' "$TS" POST /v1/refunds '' "$BODY_HASH" \
  | openssl dgst -sha256 -hmac "$API_SECRET" -binary | base64)

curl -sS https://api.paymos.io/v1/refunds \
  -H "Authorization: HMAC-SHA256 $API_KEY_ID:$SIGNATURE" \
  -H "X-Request-Timestamp: $TS" \
  -H "Content-Type: application/json" \
  -d "$BODY"
```

```javascript
import { Paymos, externalOrderId } from '@paymos/sdk';

const paymos = new Paymos({
  apiKey: process.env.PAYMOS_API_KEY,
  apiSecret: process.env.PAYMOS_API_SECRET,
});
const refund = await paymos.refunds.create({
  invoiceId: 'inv_7K2M9P4Q8R1X5Z3A0bC2dE',
  mode: 'full',
  externalOrderId: externalOrderId('refund'),
});

console.log(refund.withdrawalId, refund.status);
```

```python
import os

from paymos import Paymos

paymos = Paymos(
    api_key=os.environ["PAYMOS_API_KEY"],
    api_secret=os.environ["PAYMOS_API_SECRET"],
)
refund = paymos.refunds.create(
    invoice_id="inv_7K2M9P4Q8R1X5Z3A0bC2dE",
    mode="full",
    external_order_id="refund-1042-full",
)

print(refund["withdrawal_id"], refund["status"])
```

```php
<?php
use Paymos\Client;
use Paymos\ClientConfig;
use Paymos\IdempotencyKey;

$paymos = new Client(new ClientConfig(
    getenv('PAYMOS_API_KEY'),
    getenv('PAYMOS_API_SECRET')
));
$refund = $paymos->refunds()->create(array(
    'invoice_id' => 'inv_7K2M9P4Q8R1X5Z3A0bC2dE',
    'mode' => 'full',
    'external_order_id' => IdempotencyKey::externalOrderId('refund'),
));

echo $refund['withdrawal_id'] . ' ' . $refund['status'];
```

```go
package main

import (
	"context"
	"fmt"
	"os"

	paymos "github.com/Paymos-labs/go-sdk/v2"
)

func main() {
	client, err := paymos.NewClient(os.Getenv("PAYMOS_API_KEY"), os.Getenv("PAYMOS_API_SECRET"))
	if err != nil {
		panic(err)
	}
	refund, err := client.Refunds.Create(context.Background(), paymos.CreateRefundParams{
		InvoiceID:       "inv_7K2M9P4Q8R1X5Z3A0bC2dE",
		Mode:            paymos.RefundModeFull,
		ExternalOrderID: "refund-1042-full",
	})
	if err != nil {
		panic(err)
	}
	fmt.Println(refund.WithdrawalID, refund.Status)
}
```

```csharp
using Paymos;

using var paymos = new PaymosClient(
    Environment.GetEnvironmentVariable("PAYMOS_API_KEY")!,
    Environment.GetEnvironmentVariable("PAYMOS_API_SECRET")!);

var refund = await paymos.Refunds.CreateAsync(new CreateRefundRequest(
    InvoiceId: "inv_7K2M9P4Q8R1X5Z3A0bC2dE",
    Mode: RefundMode.Full,
    ExternalOrderId: "refund-1042-full"));

Console.WriteLine($"{refund.WithdrawalId} {refund.Status}");
```

```java
import io.paymos.CreateRefundRequest;
import io.paymos.PaymosClient;
import io.paymos.Refund;
import io.paymos.RefundMode;

PaymosClient paymos = new PaymosClient(
    System.getenv("PAYMOS_API_KEY"),
    System.getenv("PAYMOS_API_SECRET"));

Refund refund = paymos.refunds.create(new CreateRefundRequest(
    "inv_7K2M9P4Q8R1X5Z3A0bC2dE",
    RefundMode.FULL,
    "refund-1042-full"));

System.out.println(refund.withdrawalId() + " " + refund.status());
```

```ruby
require 'paymos'

paymos = Paymos::Client.new(
  api_key: ENV.fetch('PAYMOS_API_KEY'),
  api_secret: ENV.fetch('PAYMOS_API_SECRET')
)
refund = paymos.refunds.create(
  invoice_id: 'inv_7K2M9P4Q8R1X5Z3A0bC2dE',
  mode: 'full',
  external_order_id: 'refund-1042-full'
)

puts "#{refund.withdrawal_id} #{refund.status}"
```

```rust
use paymos::{CreateRefundRequest, PaymosClient, RefundMode};

let paymos = PaymosClient::new(
    std::env::var("PAYMOS_API_KEY")?,
    std::env::var("PAYMOS_API_SECRET")?,
)?;
let refund = paymos
    .refunds()
    .create(&CreateRefundRequest {
        invoice_id: "inv_7K2M9P4Q8R1X5Z3A0bC2dE".to_owned(),
        mode: RefundMode::Full,
        external_order_id: "refund-1042-full".to_owned(),
    })
    .await?;

println!("{} {}", refund.withdrawal_id, refund.status);
```

## Response (201 Created / 200 if idempotent match)

```json
{
  "withdrawal_id": "wdr_6Qm2fK8xR4vN7cT1bY9dL5",
  "invoice_id": "inv_7K2M9P4Q8R1X5Z3A0bC2dE",
  "mode": "full",
  "external_order_id": "refund-1042-full",
  "status": "created",
  "is_final": false,
  "is_test": false,
  "amount": "100.00",
  "fee": "1.00",
  "currency": "USDT",
  "network": "TRC20",
  "destination_address": "TN3W4H6rK2ce4vX9YnFQHwKENnHjoxb3m9",
  "first_sender": "TN3W4H6rK2ce4vX9YnFQHwKENnHjoxb3m9",
  "created_at": 1767225600,
  "type": "refund",
  "project_id": "prj_3F9xL2mN8pQ4rT6vW1yZ5b"
}
```

## Response fields

| Field | Type | Description |
|-------|------|-------------|
| `withdrawal_id` | string | Prefixed payout identifier (`wdr_...`) representing this refund |
| `invoice_id` | string | Prefixed invoice identifier (`inv_...`) being refunded |
| `mode` | string | Refund mode: `"full"` or `"overpayment"` |
| `external_order_id` | string | Your idempotency reference echoed back from the create request |
| `status` | string | Current status (`created`, `signed`, `pending_review`, `cancelling`, `completed`, `failed`, or `cancelled`) |
| `is_final` | boolean | `true` once the refund reaches a terminal state (`completed`, `failed`, `cancelled`) |
| `is_test` | boolean | `true` for sandbox refunds |
| `amount` | string | Exact token amount returned to the payer |
| `fee` | string? | Flat per-token network payout fee charged to the merchant balance in addition to `amount`. Omitted when zero |
| `currency` | string | Crypto asset symbol (matches the invoice's payment currency) |
| `network` | string | Blockchain network code (matches the invoice's payment network) |
| `destination_address` | string | Payout destination address (always equal to `first_sender`) |
| `first_sender` | string | Canonical sender address of the first confirmed deposit on the invoice |
| `tx_hash` | string? | On-chain transaction hash once `status` is `completed` |
| `explorer_url` | string? | Block explorer link for `tx_hash` once `status` is `completed` |
| `created_at` | integer | Unix timestamp in seconds |
| `completed_at` | integer? | Unix timestamp in seconds when the refund completed |
| `failed_at` | integer? | Unix timestamp in seconds when the refund failed |
| `cancelled_at` | integer? | Unix timestamp in seconds when the refund was cancelled |
| `type` | string | Always `"refund"` |
| `project_id` | string | Prefixed project identifier (`prj_...`) that owns the invoice |

## Idempotency

Always send a deterministic `external_order_id` for each refund attempt. Retrying `POST /v1/refunds` with the same `(invoice_id, mode, external_order_id)` returns the existing refund with `200 OK` instead of creating a duplicate payout. Reusing an `external_order_id` with a different `invoice_id` or `mode` is rejected with `409 idempotency_conflict`.

Only one active refund may be in flight per invoice at a time. You can issue an `"overpayment"` refund first and a `"full"` refund for the remaining principal after the overpayment refund reaches `completed`.

## Errors

| Code | HTTP | When |
|------|------|------|
| `payment_key_required` | 403 | The request was signed with a Payout (`rk_`) key instead of a Payment (`pk_`) key |
| `refunds_not_enabled` | 503 | Invoice refunds are disabled in this environment |
| `invoice_not_found` | 404 | `invoice_id` does not exist or is outside the API key's project scope |
| `refund_not_eligible` | 409 | The invoice is not in `paid` or `paid_over` status, or its deposits are not eligible |
| `refund_no_overpayment` | 409 | `mode` is `"overpayment"` and the invoice has no remaining overpayment balance |
| `refund_sender_unknown` | 409 | The sender address of the first confirmed deposit is unavailable |
| `refund_window_expired` | 409 | More than 14 days have passed since the invoice's last confirmed deposit |
| `refund_network_unsupported` | 409 | Payouts are not supported on the invoice's payment network |
| `refund_in_flight` | 409 | Another refund for this invoice is still in a non-terminal status |
| `invoice_already_refunded` | 409 | The invoice has already been refunded in full |
| `refund_source_inconsistent` | 409 | Invoice deposit or refund ledger history failed consistency verification |
| `insufficient_balance` | 409 | Merchant balance cannot cover `amount + fee` |

See [Error Codes](/docs/errors/codes.md) for the full catalogue.