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How to obtain the required SII certificates from the Spanish Tax Agency

FranciscoHurtado
Product and Topic Expert
Product and Topic Expert
‎2025 Apr 14 3:40 PM
3,271

The SII (Immediate Supply of Information) is a system of keeping the VAT registration books directly in the Tax Agency servers by means of  a quasi-immediate submission of the invoice VAT-relevant information.

The SII shall shall be mandatory to the following taxpayers with a monthly VAT clearance period:

  • Taxpayers registered in REDEME (Monthly VAT Return registry)
  • Large Enterprises (turnover greater than €6.010.121.04)
  • VAT Groups
  • Since 01/01/2025, the owners of fiscal warehouses of gasoline, gas oil or biofuel subject to the Hydrocarbon Tax, as well as the extracting companies or professionals
  • Other companies registered voluntarily to SII.

The content of the SII invoicing information message must be submitted in XML format. The submissions may be performed by (1) the taxpayer, (2) a representative thereof for the purposes of this process, or (3) an authorised agent, who must have a recognised electronic certificate. Applications that send information to the Tax Agency web services must be authenticated with the client’s electronic certificate.

In summary, in order to use the Tax Agency SII services, it is required to have a recognised electronic certificate accepted by the Tax Agency installed on the computer from which the information is sent. The certificate may have been issued to a Natural Person or Legal Entity. 

 

How to obtain a REAL digital certificate

Remember that for tax transactions with the Tax Agency, your Certification Authority must be one of those that have been approved, the list of which you will find in the section Organisations that Issue Digital Certificates accredited by the Tax Agency. 

The specific steps to be followed will depend on the Certification Authority that you have chosen to issue your certificate (you might need to consult the web page of the authority that you have chosen).

  • Request of the via Internet certificate.
  • Proof of identity before one of the registration offices established by the Certification Authority. The documentation to provide when verifying your identity will depend on the type of electronic certificate requested.
  • Download of the via Internet certificate.
  • Backup of the certificate.

You can check this video (in spanish):  Como obtener un certificado de la AEAT  or see here for further details.

For example, in the case your certification authority would be the FNMT (Spanish National Mint), then the steps required in order to obtaining a certificate in software format, would be:

FranciscoHurtado_1-1744124465931.png

Do all the steps:

  • Preliminary configuration (configuracion previa). Required software installation.
  • Certificate request (solicitar certificado). Upon completion of this step, a request code (código de solicitud) will be received by email. This code will be requested in the identity proof step.
  • Identity Proof (Acreditar identidad), you might choose one of the following mechanisms:
    • Online: only for company codes with Tax ID A, B, C, and D
    • Onsite at Post office.
    • Onsite at an Identity Validation Office, such as:
      • Tax Agency identification office
      • CNMV identification office
      • Navarra  Identification office
    • Certificate Download ( descargar certificado) and payment (price list)

The Root certificates will be needed as well for the system setup, so do not forget to down load them too:

FranciscoHurtado_2-1744124465939.png

 

The full details of each step can be found in the following links:

means of  a quasi-immediate submission of the invoice VAT-relevant information.

The SII shall shall be mandatory to the following taxpayers with a monthly VAT clearance period:

  • Taxpayers registered in REDEME (Monthly VAT Return registry)
  • Large Enterprises (turnover greater than €6.010.121.04)
  • VAT Groups
  • Since 01/01/2025, the owners of fiscal warehouses of gasoline, gas oil or biofuel subject to the Hydrocarbon Tax, as well as the extracting companies or professionals
  • Other companies registered voluntarily to SII.

The content of the SII invoicing information message must be submitted in XML format. The submissions may be performed by (1) the taxpayer, (2) a representative thereof for the purposes of this process, or (3) an authorised agent, who must have a recognised electronic certificate. Applications that send information to the Tax Agency web services must be authenticated with the client’s electronic certificate.

In summary, in order to use the Tax Agency SII services, it is required to have a recognised electronic certificate accepted by the Tax Agency installed on the computer from which the information is sent. The certificate may have been issued to a Natural Person or Legal Entity. 

 

How to obtain a TEST digital certificate

In order to perform tests in the Tax Agency preproduction portal for legal forms,  SII,... it is necessary to obtain a test certificate. These certificates are issued normally with a validity period of 1 or 2 years, after which they have to be obtained again.

In order to obtain these test certificates you could access the following:

  • Support page of the FNMT (Spanish National Mint) -> Certificados de pruebas todas CAs. For the SII test, you can decompress the RAR file and search for ACTIVO_EIDAS_CERTIFICADO_PRUEBAS___99999999R with extensions .cer or .p12. Password is usually 1234. (normally under Claves RSA->AC FMT Ususarios->Nuevos->Nuevo Perfil no SMIME)
  • Request the test certificate directly to the Tax Agency via technical support (catentidades@correo.aeat.es)

FranciscoHurtado_0-1757495465917.png

 

Possible errors in the use of the electronic certificate

You can check the followng website https://sede.agenciatributaria.gob.es/Sede/en_gb/ayuda/consultas-informaticas/firma-digital-sistema-...

This page explains how to solve certificate erros, such as:

 

Tax agency technical support

In case of questions it is possible to access the Tax Agency in the following link:

https://sede.agenciatributaria.gob.es/Sede/ayuda/firma-digital-sistema-clave-pin-tecnica.html

FranciscoHurtado_3-1744124465946.png

 

 

Open the link Asistencia para soporte técnico

FranciscoHurtado_4-1744124465954.png

 

Tax Id Number and Name are required to submit any question.

SAP  links

 

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