# 创建退款

> 将已付款或超额付款账单按全额或超额差额原路退回至首笔已确认充值的发送方地址。

`POST /v1/refunds`

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

**API 密钥：** `Payment`

在账单最后一笔确认入账后的 14 天内，为状态为 `paid` 或 `paid_over` 的账单创建链上退款。目标地址与退款金额均由服务端自动计算：资金原路退回至该账单第一笔确认入账的发送方地址（`first_sender`），并从商户余额中扣除 `amount + fee`。

## 请求体

| 参数 | 类型 | 必填 | 说明 |
|------|------|------|------|
| `invoice_id` | string | 是 | 属于密钥权限范围内项目的账单前缀 ID（`inv_...`） |
| `mode` | string | 是 | `"full"`（退回账单剩余可退余额）或 `"overpayment"`（仅退回超出账单应付金额的溢付部分） |
| `external_order_id` | string | 是 | 你的幂等业务单号（最长 200 个字符），在同一商户与环境下唯一 |

## 请求示例

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

## 代码示例

每个标签页均使用官方 SDK 并配置 Payment 密钥（`pk_`）。签名、序列化、安全重试与强类型错误均由 SDK 处理。

```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);
```

## 响应（201 Created / 幂等命中时为 200）

```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"
}
```

## 响应字段

| 字段 | 类型 | 说明 |
|------|------|------|
| `withdrawal_id` | string | 代表本次退款的带前缀转出 ID（`wdr_...`） |
| `invoice_id` | string | 被退款的带前缀账单 ID（`inv_...`） |
| `mode` | string | 退款模式：`"full"` 或 `"overpayment"` |
| `external_order_id` | string | 创建请求中传入并原样返回的幂等单号 |
| `status` | string | 当前状态（`created`、`signed`、`pending_review`、`cancelling`、`completed`、`failed` 或 `cancelled`） |
| `is_final` | boolean | 当退款进入终态（`completed`、`failed`、`cancelled`）时为 `true` |
| `is_test` | boolean | 沙箱退款为 `true` |
| `amount` | string | 退回给付款人的精确代币金额 |
| `fee` | string? | 除 `amount` 外从商户余额扣除的固定单币种链上转出手续费；为零时省略 |
| `currency` | string | 加密资产符号（与账单支付币种一致） |
| `network` | string | 区块链网络代码（与账单支付网络一致） |
| `destination_address` | string | 退款目标地址（始终等于 `first_sender`） |
| `first_sender` | string | 账单第一笔确认入账的标准发送方地址 |
| `tx_hash` | string? | 当 `status` 为 `completed` 时的链上交易哈希 |
| `explorer_url` | string? | 当 `status` 为 `completed` 时指向 `tx_hash` 的区块浏览器链接 |
| `created_at` | integer | 秒级 Unix 时间戳 |
| `completed_at` | integer? | 退款完成时的秒级 Unix 时间戳 |
| `failed_at` | integer? | 退款失败时的秒级 Unix 时间戳 |
| `cancelled_at` | integer? | 退款取消时的秒级 Unix 时间戳 |
| `type` | string | 固定为 `"refund"` |
| `project_id` | string | 账单所属项目的带前缀 ID（`prj_...`） |

## 幂等性

每次发起退款时都应传入确定性的 `external_order_id`。使用相同的 `(invoice_id, mode, external_order_id)` 重试 `POST /v1/refunds` 会返回 `200 OK` 和已有退款记录，不会重复出款。将同一个 `external_order_id` 用于不同的 `invoice_id` 或 `mode` 会返回 `409 idempotency_conflict`。

同一张账单同一时间只能有一笔处于非终态的退款。你可以先发起 `"overpayment"` 退回溢付部分，待其进入 `completed` 后，再发起 `"full"` 退回剩余本金。

## 错误码

| 错误码 | HTTP | 触发场景 |
|--------|------|----------|
| `payment_key_required` | 403 | 请求使用了 Payout（`rk_`）密钥而非 Payment（`pk_`）密钥签名 |
| `refunds_not_enabled` | 503 | 当前环境未启用账单退款功能 |
| `invoice_not_found` | 404 | `invoice_id` 不存在，或不在当前 API 密钥的项目可见范围内 |
| `refund_not_eligible` | 409 | 账单不处于 `paid` 或 `paid_over` 状态，或其入账记录不符合退款条件 |
| `refund_no_overpayment` | 409 | `mode` 为 `"overpayment"`，但账单没有剩余可退的溢付金额 |
| `refund_sender_unknown` | 409 | 无法获取第一笔确认入账的发送方地址 |
| `refund_window_expired` | 409 | 距离账单最后一笔确认入账已超过 14 天 |
| `refund_network_unsupported` | 409 | 账单所在支付网络不支持链上转出 |
| `refund_in_flight` | 409 | 该账单已有另一笔退款处于非终态处理中 |
| `invoice_already_refunded` | 409 | 该账单已完成全额退款 |
| `refund_source_inconsistent` | 409 | 账单入账或退款账本历史未通过一致性校验 |
| `insufficient_balance` | 409 | 商户可用余额不足以支付 `amount + fee` |

完整列表见[错误码](/zh-hans/docs/errors/codes.md)。