# sfg_correction_reference_required (/en/docs/errores/sfg_correction_reference_required)

A nota (56/61) on the Sistema de Facturación Gratuito must reference the document it modifies with a correction code.

|                |                                                               |
| -------------- | ------------------------------------------------------------- |
| **Code**       | `sfg_correction_reference_required`                           |
| **Type**       | `unprocessable_error` — Well formed, but breaks a domain rule |
| **HTTP**       | `422`                                                         |
| **Retriable?** | No                                                            |

## What to do [#what-to-do]

Set `references[n].code` to 1 (anula), 2 (corrige texto) or 3 (corrige montos). The SFG portal writes a nota's `<Referencia>` only through its correction form, so a plain reference would be dropped and the nota emitted referencing nothing. `emission_channel=mercado` writes whatever references you send.

> **Warning**
>
> Retrying the same request will fail the same way. Change the request, not the frequency.

## The envelope [#the-envelope]

```json
{
  "error": {
    "type": "unprocessable_error",
    "code": "sfg_correction_reference_required",
    "message": "…",
    "hint": "Set `references[n].code` to 1 (anula), 2 (corrige texto) or 3 (corrige montos). The SFG portal writes a nota's `<Referencia>` only through its correction form, so a plain reference would be dropped and the nota emitted referencing nothing. `emission_channel=mercado` writes whatever references you send.",
    "retriable": false,
    "doc_url": "https://docs.facturia.cl/errors/sfg_correction_reference_required",
    "request_id": "req_01K2R7Q9M4T2VB"
  }
}
```

Program against `code`, never against `message` — the prose can be rewritten, the code cannot (§5.8).

`hint` and `retriable` arrive in the response with these exact values: they are a function of `code` and come from the same dictionary `GET /v1/error_codes` serves, so the envelope and the dictionary cannot disagree. Both are English on the wire by design — one registry, one language. More in [The error envelope](/en/docs/errores).

## See also [#see-also]

- [Every code](/en/docs/errores/codigos): The full table, grouped by where you will run into it.

- [The error envelope](/en/docs/errores): The nine types, the request_id and how to handle them in practice.

The machine-readable copy of this page lives at `GET /v1/error_codes`, unauthenticated.