> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.trygrant.com/api-reference/grant-events-api/plan-fees/create-fee/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.trygrant.com/_mcp/server.

# Add a fee to a plan

POST https://api.trygrant.com/v1/plans/{id}/fees
Content-Type: application/json

Attaches a fixed (flat) or usage-based (per_unit / cost_plus) fee to a plan. The product and price can be referenced by ID or created inline in the same call. Multiple versions of a fee for the same product are allowed as long as their effective date ranges do not overlap.

Reference: https://docs.trygrant.com/api-reference/grant-events-api/plan-fees/create-fee

## Authentication

- `Authorization` header (bearer token, required) — API key obtained from the Grant dashboard

## Servers

- `https://api.trygrant.com` (Production, default)
- `http://localhost:8787` (Local development)

## Request

### Path parameters

- `id` (string, required)

### Body (application/json)

This endpoint expects a CreatePlanFeeRequest.

- `product_id` (string, optional) — Existing product to attach the fee to
- `product` (InlineProduct, optional) — Create a new product inline instead of using product_id
- `price_id` (string, optional) — Existing price to bill. The fee is attached to the price's product, so product_id/product must be omitted.
- `price` (InlinePrice, optional) — Create a new price inline instead of using price_id
- `effective_from` (string, optional, nullable) — Date the fee becomes effective (YYYY-MM-DD in the company's timezone, or ISO datetime). Null or omitted = effective immediately.
- `effective_to` (string, optional, nullable) — Date the fee stops being effective. Null or omitted = open-ended.

## Response

### 201

Fee created

- `success` (boolean, required)
- `fee` (PlanFee, required)
- `request_id` (string, required)

## Errors

### 400 Bad Request Error

Invalid request

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 401 Unauthorized Error

Unauthorized

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 404 Not Found Error

Plan not found

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 409 Conflict Error

Conflict

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

### 500 Internal Server Error

Internal server error

- `success` (boolean, required)
- `error` (ErrorResponseError, required)
- `request_id` (string, optional) — Request ID for tracing

## Types

### InlineProduct

Create a new product inline instead of using product_id

- `name` (string, required) — Product name
- `billable_metric` (InlineProductBillableMetric, optional) — Optional billable metric used to meter usage for this product
- `cost_metric` (InlineProductCostMetric, optional) — Optional cost metric; required on the product before it can carry a cost_plus price

### InlinePrice

Create a new price inline instead of using price_id

- `pricing_model` (enum, required) — flat = fixed fee, per_unit = usage-based rate, cost_plus = underlying cost with markup
  - Allowed values: `flat`, `per_unit`, `cost_plus`
- `amount` (double, optional, default: 0) — Amount charged per `denominator` units, in minor units of the denomination. Must be an integer (e.g. cents) for currency-denominated prices; may be fractional for pricing-unit denominated prices. Ignored for cost_plus.
- `denominator` (integer, optional, default: 1) — Number of usage units the amount applies to (e.g. 1000000 for per-1M-token pricing)
- `billing_mode` (enum, optional) — Defaults to in_advance for flat fees and in_arrears for usage-based prices
  - Allowed values: `in_advance`, `in_arrears`
- `cadence` (enum, optional) — Billing cadence for flat fees (defaults to monthly). Usage-based prices have no cadence.
  - Allowed values: `monthly`, `quarterly`, `yearly`, `one_time`
- `currency_code` (enum, optional) — Currency denomination. Defaults to the company's plan currency conventions (usd) when no pricing_unit_id is given.
  - Allowed values: `usd`, `eur`, `gbp`, `cad`, `aud`, `jpy`, `chf`, `cny`, `sek`, `nzd`, `mxn`, `sgd`, `hkd`, `nok`
- `pricing_unit_id` (string, optional) — Denominate the price in a custom pricing unit instead of currency
- `display_denominator` (string, optional) — Optional display label for the denominator (e.g. "1M tokens")
- `cost_plus` (InlinePriceCostPlus, optional) — Markup configuration, required for cost_plus prices

### PlanFee

- `id` (string, required)
- `plan_id` (string, required)
- `product` (PlanFeeProduct, required)
- `price` (Price, required)
- `effective_from` (string, required, nullable) — ISO 8601 timestamp the fee becomes effective
- `effective_to` (string, required, nullable) — ISO 8601 timestamp the fee stops being effective

### ErrorResponseError

- `code` (string, required)
- `message` (string, required)
- `details` (any, optional)

### InlineProductBillableMetric

Optional billable metric used to meter usage for this product

- `expression` (map from string to any, required) — Billable metric expression matching usage events

### InlineProductCostMetric

Optional cost metric; required on the product before it can carry a cost_plus price

- `expression` (map from string to any, required) — Cost metric expression matching cost events

### InlinePriceCostPlus

Markup configuration, required for cost_plus prices

- `markup_mode` (enum, required)
  - Allowed values: `multiplier`, `target_margin`
- `multiplier` (double, optional) — Cost multiplier (required when markup_mode is multiplier), e.g. 1.2 bills 120% of cost
- `target_margin` (double, optional) — Target margin between 0 and 1 (required when markup_mode is target_margin)

### PlanFeeProduct

- `id` (string, required)
- `name` (string, required)

### Price

- `id` (string, required)
- `pricing_model` (enum, required) — flat = fixed recurring/one-time fee, per_unit = usage-based rate, cost_plus = underlying cost with markup
  - Allowed values: `flat`, `per_unit`, `cost_plus`
- `amount` (double, required) — Amount in minor units of the denomination (e.g. cents) charged per `denominator` units
- `denominator` (integer, required) — Number of usage units the amount applies to
- `billing_mode` (enum, required)
  - Allowed values: `in_advance`, `in_arrears`
- `cadence` (enum, required) — Billing cadence for flat fees; null for usage-based prices
  - Allowed values: `monthly`, `quarterly`, `yearly`, `one_time`
- `currency_code` (string, required, nullable) — Currency denomination; null when the price is denominated in a pricing unit
- `pricing_unit_id` (string, required, nullable) — Pricing unit (custom credit) denomination; null when denominated in currency
- `display_denominator` (string, required, nullable) — Optional display label for the denominator (e.g. "1M tokens")
- `cost_plus` (PriceCostPlus, required, nullable) — Markup configuration for cost_plus prices

### PriceCostPlus

Markup configuration for cost_plus prices

- `markup_mode` (enum, required)
  - Allowed values: `multiplier`, `target_margin`
- `multiplier` (double, required, nullable) — Cost multiplier, e.g. 1.2 bills 120% of cost
- `target_margin` (double, required, nullable) — Target margin between 0 and 1, e.g. 0.3 for 30%

## Examples

**Request**

```json
{}
```

**Response**

```json
{
  "success": true,
  "fee": {
    "id": "cm5x9z8nv0005h85r7l9p2k6m",
    "plan_id": "cm5x9z8nv0000h85r7l9p2k1m",
    "product": {
      "id": "cm5x9z8nv0004h85r7l9p2k5m",
      "name": "Platform fee"
    },
    "price": {
      "id": "cm5x9z8nv0003h85r7l9p2k4m",
      "pricing_model": "flat",
      "amount": 5000,
      "denominator": 1,
      "billing_mode": "in_advance",
      "cadence": "monthly",
      "currency_code": "usd",
      "pricing_unit_id": null,
      "display_denominator": null,
      "cost_plus": {
        "markup_mode": "multiplier",
        "multiplier": 1.2,
        "target_margin": null
      }
    },
    "effective_from": null,
    "effective_to": null
  },
  "request_id": "req_abc123"
}
```

**SDK Code**

```python
import requests

url = "https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees"

payload = {}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees"

	payload := strings.NewReader("{}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{}"

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{}")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees', [
  'body' => '{}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = [] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api.trygrant.com/v1/plans/cm5x9z8nv0000h85r7l9p2k1m/fees")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```

> API documentation for Grant — billing infrastructure for usage-based pricing