# Previews (/en/docs/emision/previews)

Issuing is irreversible: it spends a folio — the pre-authorised sequential number a document must
carry — and produces a legal document. When the figures came from something soft — a person describing
a factura, Chile's electronic invoice, in prose; an LLM agent assembling one — you want a step that
prices it and shows it before any of that happens.

## Draft [#draft]

```bash
curl -sS https://api.facturia.cl/v1/documents/previews \
  -H "Authorization: Bearer $FACTURIA_KEY" -H "Facturia-Empresa: $EMPRESA" \
  -H "Content-Type: application/json" \
  -d '{"tipo_dte":33,
       "receptor":{"rut":"76543212-K","giro":"Venta al por mayor de alimentos",
                   "address":{"street":"Los Militares 5001, of. 302","comuna":"Las Condes","city":"Santiago"}},
       "items":[{"description":"Consultoría","quantity":2,"unit_price":500000}]}'
```

```json
{
  "id": "prev_01K2R9...",
  "preview_id": "prev_01K2R9...",
  "object": "document_preview",
  "tipo_dte": 33,
  "totals": { "net": 1000000, "exempt": 0, "iva": 190000, "other_taxes": 0, "total": 1190000 },
  "resolved_receptor": { "rut": "76543212-K", "legal_name": null, "resolution_method": "rut_exact" },
  "folio_preview": 1042,
  "folio": null,
  "emitted": false,
  "warnings": [],
  "expires_at": "2026-08-14T14:12:40Z"
}
```

A preview runs the **whole** issuing validator — the same refusals, in the same words — and then runs
none of the issuing itself.

* `folio` is `null` because none was taken.
* `folio_preview` is the folio that *would* be used, read from the counter and **not reserved**.
* It is kept for an hour and can be read with `GET /v1/documents/previews/{preview_id}`, which returns
  **what was calculated** instead of pricing it again: totals moving between being shown and being
  approved is exactly the failure this flow exists to prevent.

### `resolution_method` [#resolution_method]

It says how the receptor was identified:

| Value                 | Meaning                                                                           |
| --------------------- | --------------------------------------------------------------------------------- |
| `rut_exact`           | Identified by RUT, Chile's taxpayer id                                            |
| `anonymous`           | A boleta with no receptor                                                         |
| `needs_clarification` | You gave a name and not a RUT, so the document would go to the anonymous consumer |

In that last case, ask for the RUT. We are not going to guess one.

## Issue what was approved [#issue-what-was-approved]

```bash
curl -sS https://api.facturia.cl/v1/documents \
  -H "Authorization: Bearer $FACTURIA_KEY" -H "Facturia-Empresa: $EMPRESA" \
  -H "Content-Type: application/json" \
  -d '{"preview_id":"prev_01K2R9...","external_id":"ORD-1042"}'
```

The stored request is replayed through the normal creation path, so nothing about the issue differs
from a direct one.

> **Trap — Issuing the same preview twice returns the original document**
>
> Not a second document: a `200` instead of the `201`, without spending a new folio. That property is
> guaranteed in the database, not in a process, so it survives concurrent retries.
>
> It exists because an agent retrying a tool call is the ordinary case here, and agents rarely send an
> `Idempotency-Key`.

Alongside `preview_id` you may send only `external_id` and `metadata`. Neither of them can change an
amount, a receptor or a date: the figures that were approved are the figures that come out, and there is
no parameter that makes that false.

## When to use it [#when-to-use-it]

- [Yes](/en/docs/mcp/herramientas): When an agent assembles the document — it is the MCP server's `draft_document` → `emit_document` flow.

- [Yes](/en/docs/emision): When a person confirms on screen and you want them to see the same number that will be issued.

You do not need it when your own system already has the exact figures and sends them as a `totals`
assertion: there, `422 totals_mismatch` already protects you from the same mistake, in a single call.