# SERIES_FORMAT_INVALID_CHARACTERS

The number this series generates would contain characters the AEAT does not accept: ‹value›. Use printable ASCII characters only, without quotes, <, > or =

<Callout type="info">
**Category:** [Account settings](/errors/category/configuracion)
</Callout>

| | |
|---|---|
| HTTP status | `422` Unprocessable Content |
| Retry | After fixing the cause |

## When it happens

The numbers the series would generate contain a character the AEAT does not accept in an invoice number: only printable ASCII is allowed, except `"`, `'`, `<`, `>` and `=`.

## How to fix it

Remove those characters from the `code` or the `format`.

## Retry

Not as is: the same request fails the same way. Fix the cause described above, then send the request again, under a new `Idempotency-Key` if the body changed.

## Returned by

The operations where this code is most likely. The list is not exhaustive.

- [`POST /v1/companies/{company_id}/series`](/invoice-series/createCompanySeries)
- [`PATCH /v1/companies/{company_id}/series/{series_id}`](/invoice-series/patchCompanySeries)

## Rules that cite this code

- [NUM-008 · An invoice number fits AEAT's length and character set](/rules/numbering#num-008)

## Example response

When this error occurs, the API answers `422` Unprocessable Content with a JSON body of this shape:

```json
{
  "type": "https://docs.beel.es/errors/SERIES_FORMAT_INVALID_CHARACTERS",
  "title": "SERIES_FORMAT_INVALID_CHARACTERS",
  "detail": "The number this series generates would contain characters the AEAT does not accept: ‹value›. Use printable ASCII characters only, without quotes, <, > or =",
  "instance": "/v1/<resource>",
  "errors": [],
  "success": false,
  "error": {
    "code": "SERIES_FORMAT_INVALID_CHARACTERS",
    "message": "The number this series generates would contain characters the AEAT does not accept: ‹value›. Use printable ASCII characters only, without quotes, <, > or =",
    "details": {}
  },
  "meta": {
    "timestamp": "2026-05-21T10:00:00Z",
    "request_id": "4bf92f3577b34da6a3ce929d0e0e4736"
  }
}
```

The `type` URI is stable and always resolves to this page.

## Message

<Tabs items={["English", "Spanish", "Catalan"]}>
  <Tab value="English">{"The number this series generates would contain characters the AEAT does not accept: ‹value›. Use printable ASCII characters only, without quotes, <, > or ="}</Tab>
  <Tab value="Spanish">{"El número que genera esta serie contendría caracteres que la AEAT no admite: ‹value›. Usa solo caracteres ASCII imprimibles, sin comillas, <, > ni ="}</Tab>
  <Tab value="Catalan">{"El número que genera aquesta sèrie contindria caràcters que l'AEAT no admet: ‹value›. Fes servir només caràcters ASCII imprimibles, sense cometes, <, > ni ="}</Tab>
</Tabs>

Send the request with `Accept-Language: <es|en|ca>` to receive the message in your preferred language.

> Placeholders like `‹value›` are filled in at runtime with the actual values of your request.

## Other errors in this category

<div className="grid grid-cols-2 gap-3 not-prose">
  <Card title="ACTIVE_CANNOT_DELETE" description="Cannot delete an active series. Deactivate it first" href="/errors/ACTIVE_CANNOT_DELETE" />
  <Card title="DEFAULT_CANNOT_BE_UNMARKED" description="Cannot unmark the default series. Set another series as default first" href="/errors/DEFAULT_CANNOT_BE_UNMARKED" />
  <Card title="DEFAULT_CANNOT_DEACTIVATE" description="Cannot deactivate the default series. Set another series as default first" href="/errors/DEFAULT_CANNOT_DEACTIVATE" />
  <Card title="DEFAULT_CANNOT_DELETE" description="Cannot delete the default series. Set another series as default first" href="/errors/DEFAULT_CANNOT_DELETE" />
  <Card title="ENTITY_TYPE_INCONSISTENT_WITH_NIF" description="The entity type ‹value› does not match the NIF ‹value›: an individual is identified by a DNI or NIE, and a company or entity by a NIF that starts with a legal-form letter" href="/errors/ENTITY_TYPE_INCONSISTENT_WITH_NIF" />
</div>

## Keep exploring

<div className="grid grid-cols-2 gap-3 not-prose">
  <Card title="All Account settings errors" description="Every code in this category in one table." href="/errors/category/configuracion" />
  <Card title="Error reference home" description="Browse every category or jump to the handling guide." href="/errors" />
</div>

---

Full OpenAPI spec: https://docs.beel.es/api/openapi