> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.zip.tax/v-6-0/api-reference/merchant/set-merchant-credentials/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.zip.tax/_mcp/server.

# Set Merchant Credentials

POST https://api.zip-tax.com/merchant/credentials/set
Content-Type: application/json

Available on Enterprise PlanSets or updates TaxCloud credentials for a merchant. Credentials are encrypted at rest with AES-256-GCM. On success an asynchronous webhook notification is sent to the configured endpoint.

Reference: https://docs.zip.tax/api-reference/merchant/set-merchant-credentials

## Authentication

- `X-API-KEY` header (required) — API Key authentication via header

## Request

### Body (application/json)

This endpoint expects an object.

- `apiKey` (string, required) — TaxCloud API key to associate with the merchant. Stored encrypted at rest with AES-256-GCM.
- `connectionId` (string, required) — TaxCloud connection ID that pairs with the API key to identify the merchant's TaxCloud integration.
- `merchantId` (string, required) — UUID of the merchant whose TaxCloud credentials are being set. The merchant must be owned by the calling account.

## Response

### 200

OK

- `merchantId` (string, required) — UUID of the merchant whose credentials were set.
- `message` (string, required) — Human-readable description of the result.
- `status` (string, required) — Result status of the operation (e.g. 'success').

## Errors

### 400 Set Merchant Credentials Body Bad Request Error

Bad Request

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

### 401 Set Merchant Credentials Body Unauthorized Error

Unauthorized

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

### 403 Set Merchant Credentials Body Forbidden Error

Forbidden

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

### 409 Set Merchant Credentials Body Conflict Error

Conflict

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

### 422 Set Merchant Credentials Body Unprocessable Entity Error

Unprocessable Entity

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

### 500 Set Merchant Credentials Body Internal Server Error

Internal Server Error

- `detail` (string, optional) — A human-readable explanation specific to this occurrence of the problem.
- `errors` (list of ErrorDetail, optional) — List of individual error details
- `instance` (string, optional) — A URI reference that identifies the specific occurrence of the problem.
- `status` (long, optional) — HTTP status code
- `title` (string, optional) — A short, human-readable summary of the problem type. This value should not change between occurrences of the error.
- `type` (string, optional, default: about:blank) — A URI reference to human-readable documentation for the error.

## Types

### ErrorDetail

- `location` (string, optional) — Where the error occurred, e.g. 'body.items[3].tags' or 'path.thing-id'
- `message` (string, optional) — Error message text
- `value` (any, optional) — The value at the given location

## Examples

**Request**

```json
{
  "apiKey": "apiKey",
  "connectionId": "connectionId",
  "merchantId": "merchantId"
}
```

**Response**

```json
{
  "merchantId": "merchantId",
  "message": "message",
  "status": "status"
}
```

**SDK Code**

```python
import requests

url = "https://api.zip-tax.com/merchant/credentials/set"

payload = {
    "apiKey": "apiKey",
    "connectionId": "connectionId",
    "merchantId": "merchantId"
}
headers = {
    "X-API-KEY": "<apiKey>",
    "Content-Type": "application/json"
}

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

print(response.json())
```

```javascript
const url = 'https://api.zip-tax.com/merchant/credentials/set';
const options = {
  method: 'POST',
  headers: {'X-API-KEY': '<apiKey>', 'Content-Type': 'application/json'},
  body: '{"apiKey":"apiKey","connectionId":"connectionId","merchantId":"merchantId"}'
};

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.zip-tax.com/merchant/credentials/set"

	payload := strings.NewReader("{\n  \"apiKey\": \"apiKey\",\n  \"connectionId\": \"connectionId\",\n  \"merchantId\": \"merchantId\"\n}")

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

	req.Header.Add("X-API-KEY", "<apiKey>")
	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.zip-tax.com/merchant/credentials/set")

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

request = Net::HTTP::Post.new(url)
request["X-API-KEY"] = '<apiKey>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"apiKey\": \"apiKey\",\n  \"connectionId\": \"connectionId\",\n  \"merchantId\": \"merchantId\"\n}"

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.zip-tax.com/merchant/credentials/set")
  .header("X-API-KEY", "<apiKey>")
  .header("Content-Type", "application/json")
  .body("{\n  \"apiKey\": \"apiKey\",\n  \"connectionId\": \"connectionId\",\n  \"merchantId\": \"merchantId\"\n}")
  .asString();
```

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

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.zip-tax.com/merchant/credentials/set', [
  'body' => '{
  "apiKey": "apiKey",
  "connectionId": "connectionId",
  "merchantId": "merchantId"
}',
  'headers' => [
    'Content-Type' => 'application/json',
    'X-API-KEY' => '<apiKey>',
  ],
]);

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

```csharp
using RestSharp;

var client = new RestClient("https://api.zip-tax.com/merchant/credentials/set");
var request = new RestRequest(Method.POST);
request.AddHeader("X-API-KEY", "<apiKey>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"apiKey\": \"apiKey\",\n  \"connectionId\": \"connectionId\",\n  \"merchantId\": \"merchantId\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "X-API-KEY": "<apiKey>",
  "Content-Type": "application/json"
]
let parameters = [
  "apiKey": "apiKey",
  "connectionId": "connectionId",
  "merchantId": "merchantId"
] as [String : Any]

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

let request = NSMutableURLRequest(url: NSURL(string: "https://api.zip-tax.com/merchant/credentials/set")! 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()
```