What is SII in Spain, who does it apply to, and when does it become mandatory?
SII is the Spanish Tax Agency’s system for keeping VAT record books through the near real-time submission of invoicing records. If you build software or manage tax operations, you need to understand who it applies to, which deadlines it involves, and how it differs from Verifactu. The AEAT defines it as a system for the near immediate supply of records, not of the full invoice itself.
What is Immediate Supply of Information (SII) in Spain?
SII, or Immediate Supply of Information, is a system for electronically managing VAT record books through the AEAT’s online platform. Its purpose is to bring the timing of invoice registration or bookkeeping closer to the actual economic transaction. In practice, it is used to submit invoicing data in a structured format and improve VAT management with more up to date information.
Who does SII apply to
SII is mandatory for VAT taxpayers that file VAT returns on a monthly basis. This includes businesses registered in REDEME, large companies with annual turnover above EUR 6,010,121.04, and VAT groups. Since January 1, 2025, it also applies to certain holders of tax warehouses for petrol, diesel, or biofuels, as well as businesses that extract those products. Outside these cases, joining the system is voluntary.
When does SII become mandatory
SII has been mandatory since July 1, 2017 for the groups covered by this regime. In addition, the process involves short submission deadlines for invoicing records, which makes automated processes and a stable technical integration especially important. For many businesses, the challenge is not only regulatory but also operational.
Differences between SII and Verifactu
Although both are connected to the AEAT, they do not serve the same purpose. SII focuses on submitting VAT records for the maintenance of VAT books. Verifactu, by contrast, focuses on the technical requirements of invoicing software, such as record integrity, traceability, and immutability. Put simply, SII is about VAT reporting, while Verifactu is about how the invoicing system behaves and is controlled.
Why is it useful to adapt your software to comply with SII
Adapting your software to SII helps you reduce manual work, minimize errors, and better support customers that are already required to comply or want to opt in voluntarily. Because records must be submitted electronically and must pass specific technical validations, automating this flow improves efficiency and reduces rejections. If your solution works with ERP, POS, or invoicing systems, preparing your architecture for SII also puts you in a stronger position to coexist with other obligations such as Verifactu, TicketBAI, or NaTicket without multiplying development work.
Comply with SII with fiskaly SIGN ES
With fiskaly SIGN ES, you can integrate SII compliance through a single API and automate the submission of VAT records to the AEAT without adding a separate integration for each regulation. This helps you simplify rollouts, reduce technical effort, and scale on a stronger foundation. If you want to integrate compliance with less friction, fiskaly SIGN ES helps you implement SII with specialized technical support, pre validations, and an architecture built to grow with your product.