> ## Documentation Index
> Fetch the complete documentation index at: https://apidocs.taxwire.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Versions

> API Versioning

## Current API version

```
hydrogen.2025-04-15
```

## Version naming

We use a date & human-readable name based semantic versioning for our API. This means that we increment the named version when we make breaking changes to the API.

Version format: `named_version.YYYY-MM-DD`

Example: `hydrogen.2025-03-21`

```
hydrogen.2025-03-21 -> hydrogen.2025-04-22 ==> No breaking changes
hydrogen.2025-03-21 -> helium.2025-04-22 ==> Breaking changes
```

In order to ensure you get a response format that you expect, we recommend that you pass a version header to your API calls.

<Card title="Warning" icon="triangle-exclamation">
  If you do not provide a version header, you will get the latest version of the API which could include breaking changes since the last time you called the API.
</Card>

A version header `Taxwire-Version` is expected in the following format:

<CodeGroup>
  ```shell cURL theme={null}
  curl --request POST \
    --url https://api.taxwire.com/calculations \
    --header 'Content-Type: application/json' \
    --header 'Taxwire-Version: hydrogen.2025-04-15' \
    --header 'X-API-Key: YOUR_API_KEY' \
    --data '{....SOME BEAUTIFUL JSON....}'
  ```

  ```python Python theme={null}
  import requests

  url = "https://api.taxwire.com/calculations"
  headers = {
      "Taxwire-Version": "hydrogen.2025-04-15",
      "Content-Type": "application/json",
      "X-API-Key": "YOUR_API_KEY"
  }
  payload = {
      # ... MORE BEAUTIFUL JSON ...
  }
  response = requests.request("POST", url, json=payload, headers=headers)
  response.json()
  ```

  ```javascript JavaScript theme={null}
  const options = {
    method: 'POST',
    headers: {
      'Taxwire-Version': 'hydrogen.2025-04-15',
      'Content-Type': 'application/json',
      'X-API-Key': 'YOUR_API_KEY'
    },
    body: '{ ...GREAT JSON... }'
  };

  fetch('https://api.taxwire.com/calculations', options)
    .then(response => response.json())
    .then(response => console.log(response))
    .catch(err => console.error(err));
  ```
</CodeGroup>