## Add a product to an invoice

`POST /v1/invoices/:id/products`

Adds a single product row to an invoice. Unlike `PUT /v1/invoices/:id/products`, it does not replace existing rows.

> **Field names are validated.** A field name that is not in the writable set is not dropped silently: the request is rejected with `400 INVALID_PARAMS` and the error text lists the writable names. Read-only fields that appear in product-row responses — `priceAccount`, `ownerId`, `storeId` and others — are accepted and ignored, so an object read via `GET` can be sent back as is.

## Parameters

| Parameter | Type | Required | Description |
|----------|-----|:-----:|---------|
| `id` (path) | number | yes | Invoice ID |

## Request fields (body)

| Field | Type | Required | Description |
|------|-----|:-----:|---------|
| `productId` | number | no | Catalog product ID. If set without `productName`, the name is taken from the catalog. Catalog: `GET /v1/products` |
| `productName` | string | no | Product row name — for a free-form row with no catalog product. Specify at least one of `productId` and `productName` |
| `price` | number | no | Price per unit |
| `quantity` | number | no | Quantity |
| `discountTypeId` | number | no | How the discount is set: `1` — as an amount in `discount`, `2` — as a percentage in `discountRate`. Defaults to `2` |
| `discount` | number | no | Discount amount. Applied only when `discountTypeId` is `1` |
| `discountRate` | number | no | Discount percentage. Applied only when `discountTypeId` is `2` |
| `taxRate` | number | no | Tax rate (%) |
| `taxIncluded` | boolean | no | Tax included in the price |

## Examples

### curl — personal key

```bash
curl -X POST "https://vibecode.bitrix24.com/v1/invoices/58/products" \
  -H "X-Api-Key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "productId": 1, "price": 25000, "quantity": 2 }'
```

### curl — OAuth application

```bash
curl -X POST "https://vibecode.bitrix24.com/v1/invoices/58/products" \
  -H "X-Api-Key: YOUR_APP_KEY" \
  -H "Authorization: Bearer USER_SESSION_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{ "productId": 1, "price": 25000, "quantity": 2 }'
```

### JavaScript — personal key

```javascript
const res = await fetch('https://vibecode.bitrix24.com/v1/invoices/58/products', {
  method: 'POST',
  headers: {
    'X-Api-Key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ productId: 1, price: 25000, quantity: 2 }),
})

const { success, data } = await res.json()
console.log('Row ID:', data.id)
```

### JavaScript — OAuth application

```javascript
const res = await fetch('https://vibecode.bitrix24.com/v1/invoices/58/products', {
  method: 'POST',
  headers: {
    'X-Api-Key': 'YOUR_APP_KEY',
    'Authorization': 'Bearer USER_SESSION_TOKEN',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ productId: 1, price: 25000, quantity: 2 }),
})

const { success, data } = await res.json()
```

## Response fields

| Field | Type | Description |
|------|-----|---------|
| `data` | object | The created product row in full, HTTP status `201`. Field set — [Product fields](/docs/entities/invoices/products-fields) |

## Response example

Key fields shown. Full list — [Product fields](/docs/entities/invoices/products-fields).

```json
{
  "success": true,
  "data": {
    "id": 1465,
    "productId": 1,
    "productName": "Server equipment",
    "price": 25000,
    "quantity": 2,
    "discount": 0,
    "discountTypeId": 2,
    "taxIncluded": false
  }
}
```

## Error response example

404 — invoice not found:

```json
{
  "success": false,
  "error": {
    "code": "ENTITY_NOT_FOUND",
    "message": "Item not found"
  }
}
```

## Errors

| HTTP | Code | Description |
|------|-----|---------|
| 400 | `INVALID_PARAMS` | The body contains a field name that is not among the writable fields — see [Product fields](/docs/entities/invoices/products-fields) |
| 404 | `ENTITY_NOT_FOUND` | Invoice not found |
| 403 | `SCOPE_DENIED` | API key lacks the `crm` scope |
| 401 | `TOKEN_MISSING` | API key has no configured tokens |

Full list of common API errors — [Errors](/docs/errors).

## Known specifics

**An amount discount requires `discountTypeId: 1`.** The discount type defaults to `2`, a percentage, and in that mode the `discount` field is not stored: the row is created with `discount: 0` and no error is raised. To set a discount as an amount, send `discountTypeId: 1` together with `discount`; to set it as a percentage, send `discountRate` with type `2`.

## See also

- [Product rows](/docs/entities/invoices/products-get)
- [Set products](/docs/entities/invoices/products-set)
- [Delete a product](/docs/entities/invoices/products-delete)
- [CRM products](/docs/entities/products)