SII (Suministro Inmediato de Información)

What is SII?

SII (Suministro Inmediato de Información) is Spain's electronic VAT reporting system operated by the Spanish Tax Agency (AEAT). It requires businesses to electronically report issued invoices within 4 calendar days of issuance.

With fiskaly SIGN ES, invoices can be transmitted to AEAT via SII automatically using the same invoice API used for Verifactu or TicketBAI. No additional endpoints or invoice structures are required.

To enable SII, it simply needs to be activated in the taxpayer configuration:

sii.state = ENABLED

Once enabled, all new invoices created for that taxpayer are automatically routed to SII instead of Verifactu.

Integration Overview

No API changes required

The invoice API payload remains exactly the same when using SII. Invoices are created using the same endpoint:

PUT /clients/{client_id}/invoices/{invoice_id}

The routing depends on the taxpayer configuration:

• SII enabled → invoices are transmitted to AEAT via SII
• SII disabled → invoices follow the Verifactu flow

info

The main difference in the API response is that SII invoices do not include QR codes or fingerprints, as these are not required by SII.

SII and Verifactu

Mutual exclusivity

A taxpayer cannot use SII and Verifactu simultaneously. When SII is enabled, Verifactu transmission is automatically disabled. All new invoices will be transmitted exclusively via SII.

If needed, you can switch back to Verifactu by updating the taxpayer configuration:

PATCH /taxpayer
{
  "content": {
    "sii": {
      "state": "DISABLED"
    }
  }
}

This pauses SII transmission and reactivates Verifactu.

Infrastructure and Certificates

Signers and clients

Switching to SII does not require creating new signers or clients. The existing entities remain unchanged:

• The signer (digital certificate) remains the same
• The client (POS/register entity) remains the same
• Only the taxpayer configuration changes

The same fiskaly-managed certificate is used for both SII communication and Verifactu compliance.

Legal Requirements

Social collaborator agreement

To submit invoices via SII, the taxpayer must sign the official AEAT representation agreement:

"Modelo de Representación para el Suministro Electrónico de Registros de Facturación."

By accepting this agreement, the taxpayer authorizes fiskaly to act as their representative and submit invoice records to AEAT on their behalf. Fiskaly is able to do this as an accredited social collaborator of the Spanish Tax Agency.

info

This agreement covers SII only and is different from the Verifactu agreement (ANEXO I). Even if an agreement for enabling Verifactu is already in place, a separate SII agreement must be signed. Both agreements can coexist simultaneously.

Invoice Submission and AEAT Response

When an invoice is created:

1. fiskaly generates the SII XML request
2. The request is sent to AEAT
3. AEAT validates the invoice
4. The AEAT response is returned immediately

Possible responses include:

AEAT response	Meaning
Accepted	Invoice successfully registered with AEAT
Accepted with errors	Invoice registered but requires correction
Rejected	Invoice not registered and must be corrected and resubmitted

The AEAT response is returned in the transmission fields of the invoice API response.

Submission Timing

SII requires invoices to be reported within a maximum of 4 calendar days of issuance. fiskaly does not enforce this deadline. Invoices are transmitted immediately when the API call is made, but ensuring compliance with the legal reporting window remains the taxpayer's responsibility.

info

The issued_at field must always contain the original invoice issuance date, even if the invoice is submitted later.

Connection Loss

Unlike other regulations, the SII does not require real-time submission; instead, it has submission deadlines (generally four business days for issued invoices), so a temporary internet outage is not usually critical as long as service is restored within the deadline.

If the outage lasts longer and the submission deadline is missed, invoices can still be sent using the same mechanism even after the deadline. The applicable deadlines and any consequences of late submission are determined by the relevant regulations.

The system does not prevent the submission of invoices after the deadline. The same validation checks are applied whether the invoices are submitted on time or late. The only difference is that for submissions related to already closed periods, no reconciliation (matching) information will be provided.

Supported Territories

SII in SIGN ES is currently supported only for taxpayers located in Spanish common territory.

Supported

• Spain (AEAT jurisdiction) → SPAIN_OTHER

Not supported

• Basque Country (Araba, Bizkaia, Gipuzkoa) — In certain provinces, TicketBAI submissions automatically satisfy the equivalent SII requirements, eliminating duplicate reporting. This applies exclusively to the issued invoices ledger (libro de facturas emitidas).
• Navarre
• Canary Islands
• Ceuta
• Melilla

Taxpayers belonging to these territories cannot enable SII in SIGN ES at the moment.