Fiscal subject related
From the technical point of the view, it is generated through the RSA algorithm based on the following information:
- Date of issuing
- Date and time of the last alteration of the document
- Receipt number
- Total of the receipt (rounded to 2 decimals)
- The signature generated in the previous document, of the same series
- and on the private key of the computer invoicing program producer
It is important to state, that a digital signature needs to be recorded in the invoicing database (which cannot be encrypted), and is directly associated with the original document’s record. Also, the version of the private key (sequential integers) that was used to generate the signature of the respective document needs to be recorded.
Other news from Portugal
TLv6 Implementation Marks Significant Shift in EU’s Trust List Format
A new EU Trust List format, TLv6, will officially replace TLv5 in May 2025 as part of the updated eIDAS Regulation (EU 2024/1183). It introduces key technical changes like a new URI field, updated signature format, and optional phone number support. Organizations must update their systems to avoid signature validation failures and service disruptions, as TLv5 will no longer be valid once TLv6 take... Read more
New Certifying Entity to Issue Digital Certificates for Software Producers and Economic Operators in Portugal

The Portuguese Tax and Customs Authority announced that a new Certification Authority will go live on May 31, 2025, requiring Software Producers and Economic Operators to use 4096-bit RSA certificates for accessing AT web services. Read more
Portugal Delays B2G e-Invoicing for Small and Medium Businesses

Portugal has postponed the mandatory B2G electronic invoicing requirement for small, medium, and microenterprises from January 1, 2025, extending the compliance deadline to December 31, 2025. Until then, businesses can continue using alternative invoicing methods rather than the structured CIUS-PT e-invoicing format. Portuguese authorities have announced another postponement for the mandatory use... Read more
VIDA regulation adopted—what does that mean for business?
The EU adopted the VAT in the Digital Age (ViDA) package on March 11, 2025, introducing major changes to the VAT system starting January 1, 2027. Key reforms include mandatory digital VAT reporting by 2030, new VAT collection rules for online platforms, and expanded One-Stop Shop (OSS) registration to simplify cross-border compliance. Additional measures, such as mandatory e-invoicing, phasing out... Read more
New document was uploaded: S4F backoffice patch
S4F backoffice patch is intended for users who have already installed S4F backoffice and are intended to update existing installations to latest version. To do so apply only patches that are marked with version number that is newer than your currently installed instance of backoffice. Read more
Slovenia: EU Targets Unsafe E-Commerce Imports with New Measures
The European Commission is tightening regulations on e-commerce imports to address the surge of unsafe and counterfeit goods, particularly from China, by reforming customs rules and increasing product safety checks. Key measures include removing the duty exemption for low-value parcels, introducing a potential customs fee, establishing priority control areas, and launching an EU-wide product safet... Read more
New document was uploaded: S4F backoffice patch
S4F backoffice patch is intended for users who have already installed S4F backoffice and are intended to update existing installations to latest version. To do so apply only patches that are marked with version number that is newer than your currently installed instance of backoffice. Read more