SII Guide

Spain's Suministro Inmediato de Información (SII) is AEAT's real-time invoice reporting system for large businesses. FiscalAPI supports SII as a third Spanish fiscalization system alongside TicketBAI and Verifactu.

What is SII?

SII requires businesses to electronically submit invoice records to AEAT within four calendar days of issuance. Unlike TicketBAI (Basque Country) and Verifactu (nationwide for smaller businesses), SII targets companies with annual revenue of EUR 6 million or more.

Who must use SII?

SII is mandatory for:

Companies with annual turnover exceeding EUR 6,336,000
Businesses enrolled in the monthly VAT refund scheme (REDEME)
Groups filing consolidated VAT returns (grupos de IVA)
Businesses that voluntarily opt in

SII vs TicketBAI vs Verifactu

Feature	SII	TicketBAI	Verifactu
Scope	Large businesses (>=EUR 6M)	Basque Country only	Rest of Spain
Authority	AEAT (national)	Regional tax authorities	AEAT (national)
Protocol	SOAP 1.1	XML POST / LROE	SOAP 1.1
Authentication	Mutual TLS (qualified certificate)	Client certificate	Mutual TLS
Submission window	4 calendar days	Real-time	Real-time
Invoice chaining	No	Yes (XAdES-EPES)	Yes (SHA-256)

Book types (Libros Registro)

SII organizes invoice data into four books:

Book	Spanish name	Description
Issued invoices	Libro de Facturas Expedidas	Invoices you issue to customers
Received invoices	Libro de Facturas Recibidas	Invoices you receive from suppliers
Investment goods	Libro de Bienes de Inversión	Capital asset acquisitions
Intra-community operations	Libro de Operaciones Intracomunitarias	Cross-border EU transactions

FiscalAPI currently supports the issued invoices and received invoices books, which cover the vast majority of SII submissions.

Configuration

Country config fields

Field	Type	Required	Description
`system`	string	Yes	Must be `"sii"`
`nif`	string	Yes	Spanish tax ID (NIF/CIF) of the obligated party
`legal_name`	string	Yes	Full legal name (razón social)
`certificate_id`	string	Yes	Reference to an uploaded certificate for mutual TLS

Configuration example

curl -X POST https://api.fiscalapi.com/v1/locations \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer fsk_test_abc123def456..." \
  -d '{
    "name": "Madrid HQ",
    "country": "ES",
    "address": "Calle de Alcalá 50, 28014 Madrid",
    "tax_id": "A12345674",
    "country_config": {
      "system": "sii",
      "nif": "A12345674",
      "legal_name": "Gran Empresa SL",
      "certificate_id": "spain-sii-prod-2026"
    }
  }'

Submission flow

Issued invoices (Facturas Expedidas)

Transaction is created via POST /v1/transactions
FiscalAPI builds a SOAP envelope with the invoice record (RegistroLRFacturasEmitidas)
Envelope is submitted to AEAT via mutual TLS
AEAT responds with an EstadoEnvio (Correcto, Incorrecto, ParcialmenteCorrecto)
On success, fiscal_id is set to the CSV (Código Seguro de Verificación)
Transaction status transitions to success

Cancellations (Baja)

Voiding a transaction submits a cancellation record (TipoComunicacion = A4) to the same issued invoices endpoint.

Received invoices (Facturas Recibidas)

To submit a received invoice, set "book_type": "received" in the transaction metadata along with the counterparty details.

Transaction metadata

SII transactions accept optional metadata fields to control invoice details. All fields are optional -- FiscalAPI applies sensible defaults when omitted.

Metadata fields

Field	Type	Default	Description
`invoice_number`	string	Transaction ID	Invoice number (NumSerieFacturaEmisor)
`series`	string	--	Optional series prefix prepended to invoice number
`issue_date`	string	Current date	Invoice date in DD-MM-YYYY format
`description`	string	Auto-generated	Operation description (DescripcionOperacion)
`regime_key`	string	`"01"` (general)	Special regime key (ClaveRegimenEspecialOTrascendencia)
`exercise`	string	Current year	Fiscal year (Ejercicio)
`period`	string	Current month	Tax period: `"01"`--`"12"` or `"0A"` for annual
`simplified`	boolean	`false`	If true, generates an F2 simplified invoice
`book_type`	string	`"issued"`	`"issued"` or `"received"`

Counterparty fields

Required for standard (F1) invoices. Omit for simplified (F2) invoices.

Field	Type	Description
`counterparty_nif`	string	Counterparty NIF (domestic)
`counterparty_name`	string	Counterparty legal name
`counterparty_id_type`	string	Foreign ID document type (`"02"` = VAT number, `"04"` = passport)
`counterparty_country`	string	ISO 3166-1 alpha-2 country code
`counterparty_id`	string	Foreign identifier value

Credit note fields

Field	Type	Description
`original_invoice_number`	string	Number of the invoice being corrected
`original_issue_date`	string	DD-MM-YYYY of the original invoice

Example: standard issued invoice

curl -X POST https://api.fiscalapi.com/v1/transactions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer fsk_test_abc123def456..." \
  -d '{
    "location_id": "loc_madrid_hq",
    "type": "sale",
    "amount": 121000,
    "currency": "EUR",
    "items": [
      {
        "description": "Consulting services",
        "quantity": 1,
        "unit_price": 100000,
        "total_amount": 121000,
        "tax_rate": 2100,
        "tax_amount": 21000
      }
    ],
    "metadata": {
      "invoice_number": "FA-2026/001",
      "series": "A-",
      "issue_date": "13-03-2026",
      "description": "Consulting services Q1 2026",
      "regime_key": "01",
      "counterparty_nif": "B99999999",
      "counterparty_name": "Acme Consulting SL"
    }
  }'

Example: credit note (refund)

curl -X POST https://api.fiscalapi.com/v1/transactions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer fsk_test_abc123def456..." \
  -d '{
    "location_id": "loc_madrid_hq",
    "type": "refund",
    "amount": -121000,
    "currency": "EUR",
    "items": [
      {
        "description": "Consulting services - correction",
        "quantity": 1,
        "unit_price": -100000,
        "total_amount": -121000,
        "tax_rate": 2100,
        "tax_amount": -21000
      }
    ],
    "metadata": {
      "invoice_number": "RA-2026/001",
      "issue_date": "13-03-2026",
      "description": "Rectificación FA-2026/001",
      "counterparty_nif": "B99999999",
      "counterparty_name": "Acme Consulting SL",
      "original_invoice_number": "A-FA-2026/001",
      "original_issue_date": "10-03-2026"
    }
  }'

Invoice types

Code	Name	When to use
F1	Factura	Standard invoice (default for `sale` transactions)
F2	Factura simplificada	Simplified invoice (set `"simplified": true`)
R1	Factura rectificativa	Credit note (automatic for `refund` transactions)

Regime keys

The regime_key metadata field maps to AEAT's ClaveRegimenEspecialOTrascendencia. Common values:

Key	Description
`01`	General regime (default)
`02`	Export
`03`	Special regime for used goods
`05`	Travel agencies
`07`	Special cash accounting regime
`09`	Intra-community acquisitions

AEAT endpoints

SII communicates with AEAT via SOAP 1.1 over mutual TLS.

Production

Book	URL
Issued invoices	`https://www1.agenciatributaria.gob.es/wlpl/SSII-FACT/ws/fe/SiiFactFEV2SOAP`
Received invoices	`https://www1.agenciatributaria.gob.es/wlpl/SSII-FACT/ws/fr/SiiFactFRV2SOAP`

Sandbox

Book	URL
Issued invoices	`https://prewww1.aeat.es/wlpl/SSII-FACT/ws/fe/SiiFactFEV2SOAP`
Received invoices	`https://prewww1.aeat.es/wlpl/SSII-FACT/ws/fr/SiiFactFRV2SOAP`

Sandbox endpoints accept test submissions without affecting real tax records. Set test_mode: true on transactions to use the sandbox.

Submission deadline

Invoices must be reported to SII within four calendar days of the invoice issue date (or the accounting date for received invoices). Sundays and national holidays do not count toward this deadline.

FiscalAPI submits invoices to AEAT in real-time when the transaction is created, so you meet the deadline as long as you create the transaction within the four-day window.

Error handling

AEAT responds with one of three statuses:

Status	Meaning	FiscalAPI mapping
`Correcto`	All records accepted	`success`
`ParcialmenteCorrecto`	Some records accepted, some rejected	`partial`
`Incorrecto`	All records rejected	`failed`

Per-record errors include an error code and description. These are surfaced as warnings in the transaction response. Common errors:

1106: Invalid NIF
2000: Duplicate invoice (already registered)
3000: XML schema validation error

Certificate setup

SII requires a qualified electronic certificate for mutual TLS authentication with AEAT. Upload your certificate through the certificates API:

curl -X POST https://api.fiscalapi.com/v1/certificates \
  -H "Authorization: Bearer fsk_test_abc123def456..." \
  -F "name=spain-sii-prod-2026" \
  -F "type=pkcs12" \
  -F "file=@certificate.p12" \
  -F "password=cert-password"

Then reference the certificate ID in your location's country_config.certificate_id.

What is SII?​

Who must use SII?​

SII vs TicketBAI vs Verifactu​

Book types (Libros Registro)​

Configuration​

Country config fields​

Configuration example​

Submission flow​

Issued invoices (Facturas Expedidas)​

Cancellations (Baja)​

Received invoices (Facturas Recibidas)​

Transaction metadata​

Metadata fields​

Counterparty fields​

Credit note fields​

Example: standard issued invoice​

Example: credit note (refund)​

Invoice types​

Regime keys​

AEAT endpoints​

Production​

Sandbox​

Submission deadline​

Error handling​

Certificate setup​