## GET /api/v2/billing/invoices/{id}/payment-link

**Get invoice payment link state**

Return active and previous payment-link state for one invoice. Use this to avoid generating a new link unnecessarily; use `POST /api/v2/billing/invoices/{id}/actions/generate-payment-link` when `hasActiveLink` is false or the active URL should be refreshed.

### Related Endpoints

- `POST /api/v2/billing/invoices/{id}/actions/generate-payment-link`: Generate invoice payment link
- `GET /api/v2/billing/invoices/{id}`: Get invoice details
- `POST /api/v2/billing/invoices/{id}/actions/pay`: Pay invoice by saved card

### Headers

- `Accept`: application/json
- `Authorization`: Bearer YOUR_API_KEY
- Required API scope: `read:billing`

### Parameters

- `id` (path, string, required): Public invoice ID from `GET /api/v2/billing/invoices` `data[].id` or invoice detail. Do not invent this value; use the exact ID returned by the referenced API response. Example: `inv_01hxa3b4c5d6e7f8g9h0j1k2m3`

### Request Example

```bash
curl -X GET "https://cloud.hostup.se/api/v2/billing/invoices/inv_01hxa3b4c5d6e7f8g9h0j1k2m3/payment-link" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Accept: application/json"
```

### Response Schema

- `hasActiveLink` (boolean, optional) Example: `false`
- `paymentUrl` (string,null, optional): Present when `hasActiveLink` is true; omitted when there is no active link. Example: `https://cloud.hostup.se/billing/pay/550e8400-e29b-41d4-a716-446655440000`
- `expiresAt` (string,null, optional): Present when `hasActiveLink` is true; omitted when there is no active link. Example: `2026-05-27T12:00:00.000Z`
- `viewCount` (integer, optional) Example: `3`
- `lastViewedAt` (string, optional) Example: `2026-04-27T12:30:00.000Z`
- `previousLinks` (array<object>, optional)
- `previousLinks[].createdAt` (string,null, required) Example: `2026-04-01T09:00:00.000Z`
- `previousLinks[].expired` (boolean, required) Example: `true`
- `previousLinks[].invalidatedAt` (string,null, required) Example: `2026-04-10T09:00:00.000Z`
- `previousLinks[].invalidationReason` (string,null, required) Example: `replaced`
- `previousLinks[].views` (integer, optional) Example: `1`

### Responses

#### 200 - Invoice payment-link state.
```json
{
  "hasActiveLink": false,
  "previousLinks": []
}
```

#### 400 - Invalid request. The response body is an RFC 7807 Problem Details document.
```json
{
  "type": "https://developer.hostup.se/errors/invalid_request",
  "title": "Invalid request",
  "status": 400,
  "detail": "The request body failed validation.",
  "code": "invalid_request",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z",
  "errors": [
    {
      "pointer": "/items/0/domainName",
      "detail": "`domainName` is required.",
      "code": "invalid_request"
    }
  ]
}
```

#### 401 - Unauthorized. Authentication is required.
```json
{
  "type": "https://developer.hostup.se/errors/unauthorized",
  "title": "Unauthorized",
  "status": 401,
  "detail": "Authentication is required.",
  "code": "unauthorized",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 403 - Forbidden. The caller lacks a required scope or does not own the resource.
```json
{
  "type": "https://developer.hostup.se/errors/forbidden",
  "title": "Forbidden",
  "status": 403,
  "detail": "The caller lacks a required scope or does not own the resource.",
  "code": "forbidden",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 404 - Not found. The resource does not exist or is not owned by the caller.
```json
{
  "type": "https://developer.hostup.se/errors/not_found",
  "title": "Not found",
  "status": 404,
  "detail": "The requested resource could not be found.",
  "code": "not_found",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 429 - Rate limited. Retry after the limit resets. 429 responses include `Retry-After` seconds plus `X-RateLimit-*` headers.
```json
{
  "type": "https://developer.hostup.se/errors/rate_limit_exceeded",
  "title": "Too many requests",
  "status": 429,
  "detail": "Too many requests. Retry after the limit resets.",
  "code": "rate_limit_exceeded",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 500 - Internal error. Retry later or contact support if the issue persists.
```json
{
  "type": "https://developer.hostup.se/errors/internal_error",
  "title": "Internal server error",
  "status": 500,
  "detail": "An unexpected error occurred. Retry later or contact support if the issue persists.",
  "code": "internal_error",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```