E-Invoicing in Portugal: CIUS PT, ATCUD, QR Codes & Compliance Explained

E-invoicing in Portugal

Portugal’s tax laws, via the Autoridade Tributária (AT) and public procurement regulations, have long required electronic invoicing for transactions involving the government (B2G), with broader reforms underway. The system relies on the European standard EN 16931, via its national version called CIUS PT (often in UBL 2.1 or CEFACT format), and introduces rules for invoice format, unique codes, digital signatures, monthly reporting and archiving. This blog explains who must comply now, what the technical and legal requirements are, key deadlines, the rationale behind the system, and how a provider like Flick Network can help companies navigate the changes smoothly under Portuguese law.

What Is E-invoicing in Portugal

 E-invoicing in Portugal means issuing, submitting and storing invoices in a structured, machine readable format (CIUS PT, based on EN 16931) using certified software, rather than relying solely on paper or unstructured PDF formats. For transactions with public entities (B2G), invoices must be created in this format and transmitted through the official FE-AP platform (managed by eSPAP) or via other certified channels. E-invoices should include core invoice data, the ATCUD code (a unique sequential validation number), and a QR code for traceability.

For regular business to business (B2B) or business to consumer (B2C) transactions, the e-invoicing mandate does not currently apply, but invoices must still be produced using AT certified invoicing software and adhere to rules for data submission to the tax authority. Invoices issued as simple PDFs without structured data may still be accepted under certain conditions, but that is changing. Portugal aims to strengthen; authenticity and integrity of all invoices via Qualified Electronic Signatures (QES) or equivalent seals or EDI solutions.

PDF invoices lacking the required structure or signature, once these rules are fully in force, will no longer be considered valid electronic invoices. Portugal’s e-invoicing system also ties into its broader VAT reporting regime. Resident and non resident taxpayers must submit their invoice data periodically (typically monthly) to the tax authority using a standard format (SAF-T PT) or via real time web services.

Portugal E-invoicing Timeline and Important Dates

• 2019: Public administrations were required to be able to receive electronic invoices. All central and local government entities became capable of accepting them.

• 1 January 2021: E-invoicing became mandatory for large companies that supply public entities. Large means more than 250 employees or more than €50 million turnover or more than €43 million balance sheet.

• 2022 onward: QR code became mandatory on paper and PDF invoices generated by certified software.

• 1 January 2023: Unique ATCUD code requirement was enforced for all invoices issued from certified software.

• 1 January 2025 (planned) but postponed: Mandatory structured e-invoicing in CIUS PT format for SMEs supplying the public sector. The requirement was postponed which gave SMEs more time. SMEs may continue to issue compliant PDFs with ATCUD and QR code until a new mandatory date is set by the authorities.

• PDF acceptance extended through 31 December 2026: PDF invoices without Qualified Electronic Signature (QES) will continue to be accepted until at least the end of 2026, provided they are issued by certified software with ATCUD and a QR code.

• 1 January 2027 (expected and subject to final approval): Qualified Electronic Signature (QES) will become mandatory for PDF invoices in B2B and B2C, unless the invoice is issued in structured CIUS PT format or through an approved EDI system.

• 2027 to 2028 (expected): SAF-T full accounting reporting is anticipated to become mandatory. Final deadlines are still subject to approval and may be confirmed or amended by subsequent legislation.

Who Must Comply Under Portugal’s E-invoicing Rules

Suppliers to public entities (B2G) must issue structured e-invoices. Large enterprises have been covered since 2021. Small, medium and micro enterprises are expected to comply once the postponed SME mandate comes into effect.

All businesses, resident or non resident, that are registered for VAT in Portugal must use AT certified invoicing software that can generate invoices with ATCUD code and QR code.

For PDF invoices used mainly in B2B or B2C, businesses will soon need to adopt Qualified Electronic Signatures (QES) or an equivalent trusted seal or EDI method to ensure authenticity and integrity.

All taxpayers must submit invoice data monthly or via real time webservice through SAF-T PT or directly through the AT platform.

Technical Rules and E-invoicing Process in Portugal

• Invoice Format: B2G invoices must follow the CIUS PT standard (UBL 2.1 or CEFACT). The format is XML based, machine readable and structured.

• ATCUD and QR Code: All invoices issued from certified software must include an ATCUD code and a QR code. These ensure traceability and link invoices to tax authority data.

• Digital Signature and Authenticity: For PDF invoices in B2B or B2C, businesses will be required to apply a Qualified Electronic Signature (QES) or use a qualified electronic seal or compliant EDI method to guarantee authenticity and integrity from 1 January 2027 onward, subject to final approval.

• Transmission for B2G: Invoices to public entities must be transmitted through the FE-AP platform or another certified channel.

• Record Keeping and Archiving: Invoices must be archived digitally for up to 10 years.

• Monthly and Periodic Reporting: All taxpayers registered for VAT must periodically submit invoice data via SAF-T PT or real time API submission.

Why Portugal Introduced E-invoicing

• Auditability and Transparency: Structured invoices will enable the tax authority to continuously watch and audit businesses within hours instead of being delayed, thus reducing the incidence of fiscal fraud and increasing the effectiveness of audits.

• Standardization: The use of the European e-invoicing standard (EN 16931) helps ensure interoperability across the EU and streamlines public procurement.

• Administrative Efficiency: E-invoicing reduces paperwork, accelerates invoice validation and speeds up payment processing.

• Improved VAT Control: E-invoices improve the accuracy of VAT reporting and decrease the administrative burden of both businesses and the tax authority through the combined reporting available in the electronic formats of SAF-T (Standard Audit File – Tax) Reporting.

• Legal Validity: Properly formatted and signed e-invoices have the same legal standing as paper invoices.

How Flick Network Helps Businesses Comply in Portugal

Flick Network offers a compliance focused invoicing platform that supports companies in transitioning to Portugal’s e-invoicing requirements. The platform helps with:

• Structured Invoice Generation: Creating invoices in CIUS PT (UBL 2.1 or CEFACT) format automatically, including ATCUD, QR code and VAT data.

• Digital Signature Compliance: Applying Qualified Electronic Signatures (QES) or compliant seals or EDI for PDF invoices.

• Submission and Reporting: Transmitting B2G invoices through FE-AP and supporting SAF-T PT submissions or real time reporting for B2B or B2C.

• Archiving and Audit Trails: Storing invoices digitally for the required retention period with detailed audit logs.

• Multi Jurisdiction Support: Managing invoicing compliance across multiple countries, including Portugal, with automated data mapping and regulatory updates.

Conclusion

Portugal’s e-invoicing reforms are already reshaping how businesses issue invoices, especially in the public sector. B2B and B2C requirements are moving toward greater standardization through certified software, ATCUD codes, QR codes, digital signatures and monthly data reporting.

Although several deadlines have been postponed, particularly for SMEs and digital signature requirements, the direction is clear. Early preparation helps avoid operational problems, last minute adjustments and audit risks.

Using a compliance solution like Flick Network supports seamless issuance, validation, transmission, archiving and reporting. Adopting the system early ensures a smooth transition and keeps businesses ahead of upcoming regulatory changes.

FAQs

1. What is the Portuguese e-invoicing system (CIUS PT) and when did it start in Portugal?
    It is the national version of the European e-invoicing standard EN 16931. It began in the public sector in 2019 when all public authorities were required to be able to receive structured electronic invoices.

2. Which businesses in Portugal must issue e-invoices now?
    Suppliers to public entities must issue structured e-invoices. Large companies have been required to comply since 2021. SMEs will follow once the postponed mandate resumes. All VAT registered businesses must use AT certified invoicing software that generates ATCUD and QR code.

3. Can companies in Portugal still issue simple PDF invoices?
    Yes. For now, PDF invoices are accepted. However, they must be generated by certified software, include ATCUD and QR code, and from 1 January 2027 onward must carry a Qualified Electronic Signature (QES) or equivalent trusted seal or EDI, subject to final approval.

4. Do I still need to report invoice data to the tax authority if I use e-invoicing in Portugal?
    Yes. E-invoicing does not replace reporting obligations. Taxpayers must periodically submit invoice and VAT data through SAF-T PT or real time API.

5. How long do I need to keep electronic invoice records in Portugal?
    Invoices must be archived digitally and kept available for audit for up to 10 years.