Electronic invoicing in Portugal: What you need to know going into 2026

Victoria WabaContent Marketing Manager

1/2/20263 min read

As global commerce becomes increasingly digital, Portugal is taking significant steps to modernize its tax compliance through electronic invoicing. For B2B (Business-to-Business) and B2G (Business-to-Government) entities, understanding the current requirements is key to maintaining a smooth, compliant operation.

This guide provides a professional yet approachable overview of Portugal's e-invoicing landscape, covering mandates, formats, and crucial deadlines.

Defining the essential E-invoicing terms

Before covering the requirements, let's clarify a few essential terms you'll encounter in the Portuguese e-invoicing framework:

e-Invoicing

Electronic invoicing today is driven less by efficiency gains and more by tax compliance, as governments aim to reduce VAT fraud and gain faster access to transaction data. EU initiatives such as VAT in the Digital Age reflect this shift.

Within this context, it is important to distinguish between e-invoicing and e-reporting:

E-invoicing refers to the issuance, transmission, and receipt of invoices in a structured electronic data format, which allows for automatic electronic processing,
while e-reporting focuses on transmitting invoice data to the tax authority, often under different timelines and data requirements depending on the country.

EN 16931, CIUS-PT, and UBL 2.1

For mandated e-invoices, particularly in B2G, the required format is a structured XML based on the European Standard EN 16931. Portugal's national specification is called CIUS-PT, which is often implemented using the UBL 2.1 (Universal Business Language 2.1), an international standard for the XML structure of e-business documents. When referenced in Portugal, it specifically means the national adaptation, UBL 2.1 CIUS-PT.

e-Fatura

This is the name for the online portal managed by the Portuguese Tax Authority (Autoridade Tributária e Aduaneira, or AT). Businesses use certified software to report invoice data to this system, which also allows consumers to view and manage their reported invoices for tax deduction claims.

ATCUD and QR Code

These codes are mandatory on all invoices (paper or electronic) generated by AT-certified software.

ATCUD (Código Único do Documento, or Unique Document Code): A unique identifier for each invoice.
QR Code: A mandatory code on all invoices that facilitates validation and reporting.

Portuguese Tax Authority (AT)

The Autoridade Tributária e Aduaneira oversees VAT compliance, SAF T submissions, certified invoicing software, and everything related to invoice reporting.

Mandatory structured E-invoicing for Business to Government B2G

Driven by the EU Directive 2014/55/EU, suppliers to Portuguese public authorities must issue structured electronic invoices for all B2G transactions. These use the national CIUS-PT standard, which implements the EU e-invoicing standard (EN 16931) and commonly uses formats like UBL 2.1

Invoices must be sent through authorized channels (for example, the public FE-AP platform or other accepted delivery mechanisms).

Voluntary but regulated E-invoicing for Business to Business B2B

Structured e-invoicing is not compulsory for B2B transactions in Portugal. Companies can still issue traditional invoices (e.g., PDF) between businesses.

However, all companies must comply with tax-related invoicing rules: invoices must be issued using tax authority (Autoridade Tributária e Aduaneira, AT)-certified software, include unique identifiers (e.g., ATCUD) and QR codes, and invoice data must be reported (for example via SAF-T billing processes).

Electronic invoices, including PDFs, continue to have the same legal value as paper invoices in Portugal through 31 December 2026. Under the draft 2026 Budget, businesses can keep issuing PDF invoices without a Qualified Electronic Signature (QES), with the QES requirement only taking effect from 1 January 2027.

Until then, issuers are still responsible for ensuring the authenticity, integrity, and legibility of invoice data through appropriate internal controls, while from 2027 onward the QES will become the formal, qualified method to demonstrate these safeguards for PDF e-invoices.