# POST /api/v1/billing/addon

> Toggle Addon

- **Tag:** billing
- **Operation ID:** `toggle_addon`

## Description

Add or remove an add-on from the business's Stripe subscription.

**Request Body:**
- `addon_slug`: Add-on module slug from AddOnModule enum
- `action`: 'add' (charges prorated amount immediately) or 'remove' (effective at period end, no refund)

**Effect:**
- Adding: Stripe subscription is updated, prorated amount is charged immediately
- Removing: Item removed with no proration, takes effect at period end

**Returns:** Updated active_addons list and effective date. Refused
(400 `BILLING_023`) on a business billed under a partner agreement, whose
add-ons the agreement sets.

## Authentication

Bearer token in `Authorization` header.
Required header: `x-business-id: <business uuid>`.

## Request body

Schema: `AddonToggleRequest`

- `addon_slug` (string · required) — Add-on module slug (e.g. 'ai_pro').
- `action` (string · required) (one of: add, remove) — 'add' or 'remove'.

## Responses

### 201 — Successful Response

Schema: `SuccessEnvelope_ToggleAddonResponse_`

- `success` (boolean)
- `message` (string)
- `code` (string)
- `data` (ToggleAddonResponse)

### 401 — Unauthorized - Missing or expired token, an MCP OAuth token used against the REST API, or no access to this business

Schema: `ErrorResponse`

- `error` (string · required) — Error category: `validation_error`, `unauthorized`, `forbidden`, `not_found`, `conflict`, `rate_limited`, `server_error`, or `service_unavailable`.
- `message` (string · required) — Human-readable explanation, safe to show to end users.
- `code` (string · required) — Stable machine-readable code in `CATEGORY_NNN` form (e.g. `NOT_FOUND_006`, `AUTH_010`, `GEN_002`).
- `request_id` (string) — Correlation id for support requests. Echoes the `x-request-id` request header when one was supplied.
- `errors` (object) — Field-level validation messages keyed by field name. Present on 400/422 validation failures only.

### 403 — Forbidden - Insufficient permissions

Schema: `ErrorResponse`

- `error` (string · required) — Error category: `validation_error`, `unauthorized`, `forbidden`, `not_found`, `conflict`, `rate_limited`, `server_error`, or `service_unavailable`.
- `message` (string · required) — Human-readable explanation, safe to show to end users.
- `code` (string · required) — Stable machine-readable code in `CATEGORY_NNN` form (e.g. `NOT_FOUND_006`, `AUTH_010`, `GEN_002`).
- `request_id` (string) — Correlation id for support requests. Echoes the `x-request-id` request header when one was supplied.
- `errors` (object) — Field-level validation messages keyed by field name. Present on 400/422 validation failures only.

### 422 — Validation Error

Schema: `ErrorResponse`

- `error` (string · required) — Error category: `validation_error`, `unauthorized`, `forbidden`, `not_found`, `conflict`, `rate_limited`, `server_error`, or `service_unavailable`.
- `message` (string · required) — Human-readable explanation, safe to show to end users.
- `code` (string · required) — Stable machine-readable code in `CATEGORY_NNN` form (e.g. `NOT_FOUND_006`, `AUTH_010`, `GEN_002`).
- `request_id` (string) — Correlation id for support requests. Echoes the `x-request-id` request header when one was supplied.
- `errors` (object) — Field-level validation messages keyed by field name. Present on 400/422 validation failures only.

## Code samples

### cURL

```bash
curl -X POST 'https://api.ondayzero.com/api/v1/billing/addon' \
  -H 'Authorization: Bearer dz_your_token' \
  -H 'x-business-id: YOUR_BUSINESS_ID' \
  -H 'Content-Type: application/json' \
  -d '{
  "addon_slug": "string",
  "action": "add"
}'
```

### JavaScript

```javascript
const response = await fetch('https://api.ondayzero.com/api/v1/billing/addon', {
  method: 'POST',
  headers: {
    Authorization: 'Bearer dz_your_token',
    'x-business-id': 'YOUR_BUSINESS_ID',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
  "addon_slug": "string",
  "action": "add"
}),
});
const data = await response.json();
```

### Python

```python
import httpx

headers = {
    "Authorization": "Bearer dz_your_token",
    "x-business-id": "YOUR_BUSINESS_ID",
}

payload = {'addon_slug': 'string', 'action': 'add'}

response = httpx.post("https://api.ondayzero.com/api/v1/billing/addon", headers=headers, json=payload)
data = response.json()
```

## See also

- HTML version: https://www.ondayzero.com/docs/reference/billing/toggle-addon
- OpenAPI slice: https://www.ondayzero.com/docs/reference/billing/toggle-addon/openapi.json
- Other endpoints in **billing**: https://www.ondayzero.com/docs/reference/billing (markdown bundle: https://www.ondayzero.com/docs/reference/billing.md, OpenAPI: https://www.ondayzero.com/docs/reference/billing/openapi.json)
- Endpoint catalog: https://www.ondayzero.com/docs/reference/index.md