SII — Suministro Inmediato de Informacion del IVA

SII is Spain's pioneering near-real-time VAT reporting regime. Live since 1 July 2017, it forces large taxpayers and VAT groups to transmit their VAT books to AEAT within 4 working days through a SOAP web service. It foreshadowed Verifactu and influenced ViDA at EU level.

Legal framework: Real Decreto 596/2016

SII was created by Real Decreto 596/2016 of 2 December 2016 amending the Reglamento del Impuesto sobre el Valor Anadido (Real Decreto 1624/1992). Detailed technical specifications (XML, web service, error codes) are carried by Orden HFP/417/2017 of 12 May 2017 (BOE n. 116 of 15 May 2017).

• Real Decreto 596/2016 — establishes the new "telematic VAT books" replacing (for SII taxpayers) the traditional paper books. Also removes for SII taxpayers the Modelo 347 (operations > EUR 3,005.06) and Modelo 390 (annual VAT summary) filings.
• Orden HFP/417/2017 — technical annex: XSD, WSDL, error-code table, production and pre-production endpoints.
• Law 11/2021 (anti-fraud) — strengthens SII controls and lets AEAT impose dereliction penalties (failure to transmit) retroactively over 4 fiscal years.

Scope: who must use SII?

SII is mandatory for four populations defined in article 62.6 of the Reglamento del IVA:

1. Large companies — taxable persons whose previous-year turnover (article 121 LIVA) exceeds EUR 6,010,121.04. About 27,000 companies according to AEAT.
2. VAT groups — corporate groups that have opted into the special group regime (articles 163 quinquies LIVA and following). Around 1,800 groups representing 5,000+ entities.
3. REDEME-registered — Registro de Devolucion Mensual del IVA (article 30 RIVA), the monthly VAT refund regime. About 28,000 taxpayers, mostly exporters and free-zone operators.
4. Voluntary opt-in — any company can opt into SII (Modelo 036 box 143). The election commits for the full calendar year and is tacitly renewed.

The 4 registers and their sub-books

SII organises submissions along 4 historical registers (transposed into XML by RD 596/2016), each split into sub-books:

RD 596/2016 also removes the Modelo 340 (annual book) filing for SII taxpayers and lightens the Modelo 303 (periodic VAT return) which is pre-filled from the SII books.

Transmission deadlines

Deadlines are the most demanding aspect of SII. They are computed in working days (Monday to Friday, excluding national and autonomous public holidays):

• Issued invoices: 4 working days between issue date and SII transmission date.
• Received invoices: 4 working days between bookkeeping date and SII transmission date.
• Intra-EU operations: 4 working days after transport or shipment of the goods.
• End-of-period tolerance window: until the 16th of month N+1 for month N operations (monthly closing regularisation).
• Third-party-issued invoices (factoring, outsourced billing): 8 working days instead of 4.

AEAT SOAP web service and XML schemas

SII exposes its interfaces through versioned SOAP web services. The production environment lives on www1.agenciatributaria.gob.es, pre-production on prewww1.aeat.es. Authentication is by qualified eIDAS client TLS certificate (FNMT-RCM, Camerfirma, ANCERT, Firmaprofesional, etc.).

POST /wlpl/SSII-FACT/ws/fe/SiiFactFEV1SOAP HTTP/1.1
Host: www1.agenciatributaria.gob.es
Content-Type: text/xml; charset=utf-8
SOAPAction: ""

<?xml version="1.0" encoding="UTF-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
                  xmlns:sii="https://www2.agenciatributaria.gob.es/static_files/common/internet/dep/aplicaciones/es/aeat/ssii/fact/ws/SuministroLR.xsd"
                  xmlns:siiR="https://www2.agenciatributaria.gob.es/static_files/common/internet/dep/aplicaciones/es/aeat/ssii/fact/ws/SuministroInformacion.xsd">
  <soapenv:Header/>
  <soapenv:Body>
    <sii:SuministroLRFacturasEmitidas>
      <sii:Cabecera>
        <siiR:IDVersionSii>1.1</siiR:IDVersionSii>
        <siiR:Titular>
          <siiR:NombreRazon>Atelier Iberica SL</siiR:NombreRazon>
          <siiR:NIF>B12345678</siiR:NIF>
        </siiR:Titular>
        <siiR:TipoComunicacion>A0</siiR:TipoComunicacion>
      </sii:Cabecera>
      <sii:RegistroLRFacturasEmitidas>
        <siiR:PeriodoLiquidacion>
          <siiR:Ejercicio>2026</siiR:Ejercicio>
          <siiR:Periodo>03</siiR:Periodo>
        </siiR:PeriodoLiquidacion>
        <sii:IDFactura>
          <siiR:IDEmisorFactura>
            <siiR:NIF>B12345678</siiR:NIF>
          </siiR:IDEmisorFactura>
          <siiR:NumSerieFacturaEmisor>F-2026-0042</siiR:NumSerieFacturaEmisor>
          <siiR:FechaExpedicionFacturaEmisor>15-03-2026</siiR:FechaExpedicionFacturaEmisor>
        </sii:IDFactura>
        <sii:FacturaExpedida>
          <siiR:TipoFactura>F1</siiR:TipoFactura>
          <siiR:DescripcionOperacion>Consulting services</siiR:DescripcionOperacion>
          <siiR:Contraparte>
            <siiR:NombreRazon>Cooperativa Vitoria SCoop</siiR:NombreRazon>
            <siiR:NIF>B87654321</siiR:NIF>
          </siiR:Contraparte>
          <siiR:TipoDesglose>
            <siiR:DesgloseFactura>
              <siiR:Sujeta>
                <siiR:NoExenta>
                  <siiR:TipoNoExenta>S1</siiR:TipoNoExenta>
                  <siiR:DesgloseIVA>
                    <siiR:DetalleIVA>
                      <siiR:TipoImpositivo>21</siiR:TipoImpositivo>
                      <siiR:BaseImponible>1000.00</siiR:BaseImponible>
                      <siiR:CuotaRepercutida>210.00</siiR:CuotaRepercutida>
                    </siiR:DetalleIVA>
                  </siiR:DesgloseIVA>
                </siiR:NoExenta>
              </siiR:Sujeta>
            </siiR:DesgloseFactura>
          </siiR:TipoDesglose>
          <siiR:ImporteTotal>1210.00</siiR:ImporteTotal>
        </sii:FacturaExpedida>
      </sii:RegistroLRFacturasEmitidas>
    </sii:SuministroLRFacturasEmitidas>
  </soapenv:Body>
</soapenv:Envelope>

The service always responds in two stages: an immediate synchronous acknowledgement with the global state (Correcto / AceptadoConErrores / Incorrecto), then, by polling, the per-line status. AEAT publishes an exhaustive tabla de errores:

# Main SII error codes (AEAT v1.1 technical annex)
1003  Subject out of SII scope (NIF not eligible)
1100  Invalid header
1101  Invalid period (month > 12, future, before opening)
1102  Invalid communication type (expected A0, A1, A4, A5)
1110  Duplicate invoice identifier (already submitted)
1140  Invalid electronic key (certificate authentication)
3000  Issuer NIF inactive in the AEAT register
3001  Recipient NIF unknown (VIES invalid for intra-EU)
3100  Inconsistent VAT breakdown (sum of bases != invoice total)
3110  Tax rate not allowed (outside 0/4/10/21)
4000  Deadline exceeded (>4 days after issue or >8 retro days)
5000  Invalid date format (expected DD-MM-YYYY)
9999  Internal AEAT error - retry

Coexistence with Verifactu and TicketBAI

Three regimes coexist and their articulation is key to avoiding double transmissions:

• SII (national, AEAT) — for large taxpayers and VAT groups, persists alongside Verifactu. SII remains more detailed than Verifactu (full book, not just the huella).
• Verifactu (national, AEAT) — for SMBs and self-employed outside SII and outside foral territories. SII taxpayers are exempt.
• TicketBAI (Basque Country) — for taxpayers domiciled in Bizkaia / Gipuzkoa / Araba. A large Basque taxpayer may be subject to SII for its common-regime operations (e.g. intra-EU acquisitions from non-Basque suppliers) AND to TicketBAI for its foral-regime operations.

Cross-links

• Spain hub — full e-invoicing mandate overview
• Verifactu — national equivalent outside large taxpayers
• TicketBAI — Basque foral equivalent
• Law 18/2022 Crea y Crece — B2B mandate
• Spanish VAT regimes
• Real Decreto 596/2016 (BOE)
• AEAT — SII portal