Get your SII purchase and sales register through an API

What you can build on SII

• Get the Registro de Compras for a period

  Build this

  Opens the Registro de Compras y Ventas, picks the company and tax period, presses Consultar and reads the Registro area of COMPRA.

  Takes

  Company RUT, tax period (month and year)

  Returns

  Purchase type, document type, supplier RUT, business name, folio, document date, net amount, VAT, total

• List invoices waiting in Pendientes

  Build this

  Reads the Pendientes area of COMPRA: received invoices still waiting for a recibo de mercaderías o servicios (receipt of goods or services).

  Takes

  Company RUT, tax period

  Returns

  Document type, supplier RUT, business name, folio, document date, received at SII, total

• Check claims on an invoice you issued

  Build this

  Looks up an issued invoice in the Registro de Aceptación o Reclamo de un DTE and reads the events the buyer registered on it.

  Takes

  Document type, folio

  Returns

  Folio, document type, buyer RUT, events (action, date), claimed or accepted

• Accept or claim a received invoice

  Build this

  In the Registro de Aceptación o Reclamo de un DTE, registers Acuse Recibo, Acepta contenido or one of the three reclamos on a received invoice.

  Takes

  Supplier RUT, document type, folio, action

  Returns

  Folio, supplier RUT, action registered, result message

Automate SII with a workflow

A workflow runs your methods as one process, with nobody at the screen. A schedule or a call from your own system starts it, the steps run in order, and the result arrives in your inbox or in the systems you already use.

• New invoices in Pendientes, before the 8 days run out

  Build this

  Starts

  Every weekday at 8:00

  Step 1

  List the invoices in Pendientes for the current tax period.

  Step 2

  Keep the ones that were not there on the last run.

  Step 3

  Email you the list with supplier, folio, date received at SII and total.

• Claims on the invoices you issued, to your ERP

  Build this

  Starts

  When your system calls the workflow's webhook with the invoices you issued this week

  Step 1

  For each invoice, check its claims in the Registro de Aceptación o Reclamo de un DTE.

  Step 2

  Keep the invoices with a reclamo, or with a change since the last run.

  Step 3

  Post folio, buyer RUT, action and date to your ERP webhook.

• Last month's Registro de Compras, handed to accounting

  Build this

  Starts

  On the 3rd of every month at 9:00

  Step 1

  Get the Registro de Compras for the previous tax period.

  Step 2

  Group the documents by purchase type and supplier with an AI step.

  Step 3

  Post the documents and the totals to your accounting system's webhook.

You can run a workflow by hand on every plan, Free included. Schedules and webhook triggers come with the paid plans, from $29 a month.

Once built, one call from your code

Once you have built a method, it is one POST to /v1/runs from your backend, or a tool an AI agent calls over MCP. This is what “Get the Registro de Compras for a period” would look like.

curl https://api.fous.com/v1/runs \
  -H "Authorization: Bearer $FOUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "method": "sii.cl/get_purchase_register",
    "input": {
      "company_rut": "76.543.210-3",
      "period": "2026-10"
    }
  }'

{
  "status": "completed",
  "data": {
    "company_rut": "76.543.210-3",
    "period": "2026-10",
    "documents": [
      {
        "purchase_type": "Del Giro",
        "document_type": 33,
        "supplier_rut": "77.111.222-5",
        "business_name": "Northwind Ltda.",
        "folio": 18342,
        "document_date": "2026-10-06",
        "net_amount": 1250000,
        "vat": 237500,
        "total": 1487500
      }
    ],
    "count": 1
  }
}

An example with invented data, not a ready-made endpoint. The method exists in your organization once you build it, and its name, inputs and fields follow your request.

SII’s own options

SII documents a web service that consults or registers the acceptance or claim of a received electronic invoice, for the issuer, the receiver or the current holder, signed in with a digital certificate. Electronic invoicers with a certificate can also send DTEs to SII. The Registro de Compras y Ventas is used on the site, where summaries and detail are downloaded.

Read on November 12, 2026: Web Service de Consulta y Registro de Aceptación/Reclamo a DTE, Sistema de facturación de mercado, ¿Qué es el Registro de Compras (RC)?.

Signing in to SII

SII signs you in to the Registro de Compras y Ventas with your RUT and Clave Tributaria, with Clave Única or with a digital certificate. A user authorized for several companies picks one company RUT for each operation. With Fous you sign in once through SII's own sign-in with your own RUT and Clave: the login is sealed with AES-256, and an expired session is signed back in.

Worth knowing

8 days to accept or claim

A buyer can act on an electronic invoice for 8 days from its receipt at SII. After 8 calendar days with no action, the invoice is presumed accepted irrevocably.

Acuse de recibo and reclamo exclude each other

Once you give Acuse Recibo on an invoice you cannot claim it afterwards, and once you claim it you cannot give Acuse Recibo. A write method should run only on invoices someone has checked.

Large downloads arrive later

Descargar Resúmenes and Descargar Detalles are not always immediate. The file is then kept in Descargas Diferidas, to download when it is ready.

The F29 proposal updates the next day

Non-electronic documents loaded into the Registro de Compras show at once, but reach the F29 proposal the next day. A new CSV upload replaces all non-electronic documents loaded before.

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