SII in Spain: What It Is, Who Must Comply, and How It Works

SII has changed the way Spanish businesses report and manage their VAT. The Immediate Information Supply or Suministro Inmediato de Información (SII) is Spain’s near-real-time VAT ledger reporting system. Qualified businesses are required to submit their billing records to AEAT in a structured format.

The AEAT introduced Immediate Information Supply, a digital VAT reporting system, in 2017. Its purpose is to modernise and strengthen VAT records to ensure transparency in transactions.

Key Takeaways

1. “Immediate Supply of Information" or Suministro Inmediato de Información is Spain's real-time VAT reporting system, run by AEAT, the Spanish Tax Agency.
2. AEAT requires businesses to submit structured B2B electronic invoice data within four calendar days of issuance or receipt.
3. The invoices must be submitted electronically via a web service using XML files. Businesses can create these XML files by using an e-invoicing service provider.
4. SII came into force with the approval of Royal Decree 596/2016 on December 6. It was made mandatory on July 1, 2017.

What is Suministro de Información Inmediata (SII) in Spain? 

It is a system to manage VAT records based on the Immediate Supply of Information (SII). It’s basically the electronic transmission of billing records from VAT books to Spain’s Tax Authority, AEAT. 

Eligible taxpayers must send their VAT bill details to SII within four days of issuance or receipt of the actual bills. The taxpayers don’t have to send the actual bills to AEAT. They need to send only VAT records in XML format with structured fields as required by AEAT for tax monitoring.

E-invoicing in Spain consists of three systems, and SII is one of them. It aims to solve challenges of traditional VAT reporting. It does so by creating a more transparent ecosystem.

The Immediate Information Supply, or Suministro Inmediato de Información in Spain (SII), came into effect on July 1, 2017, as Spain’s digital VAT reporting platform. Before this, VAT reporting worked the traditional way, wherein you filed periodic returns summarising a quarter or a year's worth of transactions. 

SII doesn’t replace that after-the-fact model; instead, it serves as assistance. Now, businesses must file VAT returns, but they also must transmit individual VAT records to AEAT. The VAT ledgers essentially build themselves, in near real time, on AEAT's servers. 

What SII is NOT

It's worth being precise about what SII is not. It is not a clearance system by the Spain government’s tax authority - AEAT. And, it doesn't approve or reject an invoice before it can be issued to a customer.

Moreover, it's not the same as Spain's upcoming B2B e-invoicing mandate in 2027. SII is independent of VeriFactu and Crea y Crece as it’s only a VAT data-reporting obligation. The businesses can still issue invoices the normal way. 

The only thing that changes with SII is how quickly and in what format the VAT data is transmitted to the tax authority.

SII Spain Requirements - Who Needs to Comply

All taxpayers obligated to self-assess and file their VAT monthly must comply with SII Spain.

Mainly, it’s mandatory for four categories of businesses as established by Orden HFP/417/2017, Art. 1, and confirmed in the AEAT's general SII Spain information:

Large Enterprises (Grandes Empresas)

Businesses with an annual turnover (volumen de operaciones) exceeding €6,010,121.04 in the prior calendar year, and calculated in accordance with Article 121 of LIVA. This is the largest category of mandatory SII taxpayers and the one most relevant to multinational enterprises operating in Spain.

VAT Groups (Grupos de IVA)

Entities registered under Spain's VAT group regime as a whole are the SII obligado, not the individual entities within it. It means entities that file taxes on a consolidated basis must submit electronic records of all their transactions.

REDEME Members (Monthly VAT Return Registry)

Taxpayers registered in the Monthly VAT Return Registry (Registro de Devolución Mensual del IVA). 

Fuel Deposit Holders

Holders of tax warehouses for gasoline, diesel or biofuels under the Hydrogen Tax, and professionals who extract these products from such fiscal warehouses. This category was most recently incorporated into SII’s mandatory scope.

In addition to these categories, the regulation also allows any company or professional to voluntarily opt in to the SII:

Non-Established Taxpayers

Non-established businesses with a monthly liquidation period within the Spanish VAT territory (TAI) are also subject to this obligation. It specifies a limited exception for those whose only Spanish operations are exempt intra-EU acquisitions under Articles 26.3 and 26.4 LIVA and who do not file Modelo 303.

Voluntary Opt-In

Taxpayers who are not otherwise obligated may also voluntarily opt in for SII. They can do so at any time by filing Modelo 036 (casillas 143 and 532, page 5), and the commitment must be for a full calendar year. 

SII takes effect from the first day of the liquidation period following the period in which the option was exercised. The minimum commitment is the full calendar year. Renunciation requires filing Modelo 036 in November of the prior year.

Foral Regime Note

Foral Regime Note (Regimen Foral) is a financial and administrative system to give wider tax autonomy to the Basque Country and Navarra in Spain.

Taxpayers having a fiscal domicile in the Basque Country or Navarra need not apply to SII through AEAT rules. They can apply under their own foral normativa, not directly under AEAT rules. From 2026, Basque Country taxpayers with total turnover exceeding €12 million, of which at least 75% is in territorio común, apply SII under state rules.

The Canary Islands (IGIC), Ceuta, and Melilla are outside the scope of mainland IVA and SII entirely.

What Data Must Be Reported Under SII?

The submission of VAT registration books to SII is done almost immediately. In this case, the presentation must be made within a maximum of 4 days from the invoice's accounting registration.

Businesses have to send their VAT invoices to SII in structured data organised into four VAT ledger books. The invoices should have the mandatory data fields:

Invoice-level details, like invoice issue date, number and series, VAT rate, gross amount, and counterparty’s NIF. AEAT requires all such core facts to be mentioned in each invoice. 

Investment goods must have fields for the asset description, annual deductions, and date of its first use.

How Does SII Work? 

From 1st July 2017, AEAT requires businesses to submit their VAT records on the Immediate Information Supply (SII) using XML format.

Here Is a Step-By-Step Process of How SII Works

Step 1- Transaction and Invoicing

The process begins when a transaction happens, and an invoice is issued or received by a business. After every transaction and invoice exchange, businesses send the data in an XML file to AEAT within 4 working days.

For issued invoices, the process begins on its issuance date. For a received invoice, it begins when it’s entered into the accounting system. The invoice entered into the accounting system must be submitted within a 4-day window. 

VAT invoice submission in structured XML files conforms to AEAT’s specifications.

Step 2: Data Extraction and Structure

Only the relevant invoice data is extracted into an XML format. The invoice data must follow the Spain SII schema as produced on the AEAT Sede Electronica.

Only the specific invoicing record fields outlined in Ministerial Order HFP/417/2017 must be extracted into the MAL message. It includes the number or series, date of issue, date of transaction, name and surname, company name, recipient’s tax identification number (NIF), taxable base, VAT rate, and charge from the book.

AEAT uses a combination of 3 fields: NIF of issuer, invoice series & number, & date of issue, to identify, match, and update records.

Step 3: Submission to AEAT

The taxpayers must submit only the specific invoicing fields outlined in Order HFP/417/2017. This method is meant to support high-volume automated submission and real-time validation from AEAT.

Such structured XML messages are sent via SOAP-based web services through AEAT Sede Electronica. One important point to note is that submissions can be made in a maximum of 10,000 in a single batch.

For those not having a considerable invoice volume, an alternate manual submission through the AEAT portal is available. They can use a web form on the AEAT Sede Electronica and manually submit their VAT data. 

Step 4: Processing and Response by AEAT

The Spanish government’s tax authority, AEAT, processes the invoice data and responds in real time. The response by AEAT is an XML message. Every response to the invoice data is classified under one of three statuses:

• Aceptado — accepted without issues.
• Aceptado con errores — accepted but with one or more non-blocking validation warnings.
• Rechazado — rejected due to a blocking error.

Moreover, to provide legal proof of every accepted record, AEAT provides a CSV (Código Seguro de Verificación) and a timestamp.

Step 5: Correction of Invoice Errors and Resubmission

Businesses must monitor the feedback from the AEAT and review it. It helps correct the rejected invoices and resubmit them. All of it must be done within the deadline. 

Such corrected invoices must have the same unique key with 3 elements: the issuer's NIF, series number, & date.

SII vs VeriFactu vs VAT Filing Forms

Before the introduction of Suministro Inmediato de Información (SII) in Spain, VAT Form 340 (Modelo 340) was used by large businesses to submit their VAT books of issued & received invoices. Now, the rollout of SII has made the Modelo 340 obsolete.

Companies that electronically submit their VAT records to AEAT using SII are exempt from filing VAT Forms 340, 347, and 390. 

SII vs VeriFactu: Key Differences Between SII and VeriFactu

Two e-invoicing compliance obligations, Suministro Inmediato de Información (SII) and VeriFactu, are at the centre of the shift in Spain tax compliance.

• SII: Immediate Information Supply (SII) concerns VAT ledger reporting; VeriFactu requires certified invoice generation, and both are interconnected. 
• VeriFactu: Eligible businesses must transmit their VAT records to AEAT via SII, and VeriFactu ensures that those invoices are stored in traceable systems. Businesses must maintain such compliant systems. VeriFactu establishes the integrity and immutability of the invoicing software within the business

Let’s understand the key differences among SII, VeriFactu, & VAT forms and clarify the most misunderstood areas of Spanish tax compliance:

How SII Relates to Spain's E-Invoicing Framework

SII fits well within Spain's evolving tax compliance framework, which comprises three parallel regulations: SII, VeriFactu, and Crea y Crece.

SII (Live since 2017)

It’s mandatory for large enterprises, REDEME, and VAT groups to report VAT in near-real time. It requires the VAT data to reach AEAT within 4 working days of the transaction.

VeriFactu/SIF (Live from 2026–2027)

It governs the invoice format and integrity of the invoice software. It requires that invoicing software must function and produce hash chains, QR codes, and tamper-proof records for every invoice. Applies to all businesses using SIF software, except SII taxpayers.

Compliance deadlines for VeriFactu begin in phases, with 1 January 2027 as the first phase for businesses with turnover exceeding 8 million euros. All other taxpayers are required to do so from 1 July 2027 (as updated by RD 254/2025, BOE-A-2025-6600).

Crea y Crece B2B E-Invoicing Mandate (Rolling out 2027–2028)

It’s a mandatory structured electronic B2B invoice exchange between Spanish-established businesses. It governs invoice format and transmission in B2B transactions, replacing traditional invoice exchange with structured electronic submission in the Facturae format.

SII vs the Crea y Crece B2B Mandate - Are They the Same?

SII and Crea y Crece have different legal bases and scopes under Spain’s e-invoicing landscape.

What’s SPFE in Spain’s B2B E-Invoice Exchange?

It’s a B2B e-invoice exchange platform. The AEAT will develop the SPFE - Solución Pública de Facturación Electrónica, as a public e-invoicing platform. Businesses can issue and receive structured electronic invoices through SPFE, which also serves as a repository of e-invoices in Spain.

It differs from SII as it’s the electronic exchange of invoices, whereas SII is about VAT ledger reporting to the government. 

What are the Technical & Compliance Requirements for SII?

Businesses subject to SII must submit their VAT invoice records and follow the technical & compliance requirements outlined by AEAT.

Records Submission Format

The VAT records are submitted to SII in accordance with the SII XML schema defined in Orden HFP/417/2017, Annex I. The exchange of such records is carried out via SOAP-based web services through the AEAT Sede Electronica.

The following are the required data fields:

• Batch size: Up to 10,000 invoice records per synchronous call
• Character encoding: UTF-8
• Unique record key: NIF of the issuer + Invoice series and number + Date of issue
• Alternative channel: Web form on the AEAT Sede Electrónica for low-volume taxpayers

Authentication and digital certificates

Access to the SII web services requires a valid certificado electrónico reconocido (recognised electronic certificate), including DNI-e. The NIF on the certificate must match the NIF of the book-register holder.

ERP integration requirements

For any enterprise, the practical challenge is building the data pipeline from the ERP to AEAT. The key integration requirements are:

Invoice data extraction: The ERP must be able to extract all mandatory SII fields (invoice type key, special regime key, tax base, IVA rate, quota, recipient NIF, etc.) at the moment of posting.

Accounting entry date capture: For received invoices, the accounting entry date (fecha de registro contable) must be captured as the SII clock trigger.

XML generation: The extracted data must be formatted into the XML schema.

SOAP transmission: The XML message must be transmitted to the AEAT web service endpoint with the correct certificate authentication.

Response handling: The system must process AEAT's real-time XML response, log the CSV for accepted records, and flag rejected or error records for correction.

Correction workflow: A process must exist to correct rejected records and resubmit within the deadline.

ERP systems such as SAP, Oracle, and Microsoft Dynamics require either native SII connectors or middleware integration to meet these requirements. The 4-day deadline leaves no room for manual processes at scale.

Key reconciliation checks:

Total issued invoice count and value per period (ERP vs AEAT mirror)

Total received invoice count and deductible quota per period

Rejected SII records that were not corrected within the deadline

Records accepted with errors that may indicate systematic data quality issues

What are the Penalties for Non-Compliance with SII?

Non-compliance with SII obligations and failure to meet the 4-day submission deadline will result financial in penalties. Additionally, submitting inaccurate or incomplete records will invite increased scrutiny from AEAT. Such penalties are calculated for each record and accumulate multi-fold for high taxpayers.

• Penalty for Late Submission: A penalty of 0.5% of the amount of missed invoices will be imposed for late VAT reporting to SII. A minimum of €300 and a maximum of €6,000 per quarter is set out for such penalties.
• Penalty for Wrong Submission: Every incorrect submission will incur a penalty equal to 1% of the misreported amount, with a minimum of €150 and a maximum of €6,000.
• Investment Goods: Errors in the investment goods register or the intra-community transactions register cause a fixed penalty of €150.
• Complete Non-Compliance: If a required business remains non-compliant and submits no SII data, it can incur a penalty of 1% of annual turnover.

Conclusion 

AEAT, Spain's tax authority, built SII as one of the most sophisticated near-real-time VAT monitoring systems in Europe. SII is not just a VAT filing obligation; it’s also an operational obligation. The businesses that treat SII as an operational capability are the best positioned ones for what comes next.