Essential Invoicing Obligations in 2026: ATCUD, QR Code, and SAF-T

The Portuguese tax system has been progressively digitalised and modernised, with the aim of increasing transparency and effectiveness in combating tax fraud. In this context, ATCUD, the QR Code, and invoicing SAF-T represent the backbone of the current invoicing regime in Portugal. Understanding and correctly applying these obligations are crucial for any entity that issues invoices or fiscally relevant documents.

ATCUD: The Unique Document Identifier

The Unique Document Code (ATCUD) is one of the most significant measures implemented in recent years to strengthen control over commercial operations. Its mandatory nature, in force since 01/01/2023 (having been postponed from 2022 by Dispatch No. 351/2021-XXII of the Secretary of State for Tax Affairs), stems from Ordinance No. 195/2020, of 13 August, and Decree-Law No. 28/2019, of 15 February. The ATCUD consists of two distinct parts:

• Series validation code: This code is assigned by the Tax and Customs Authority (AT) when the document series is communicated in advance on the Tax Portal. The prior communication of series is a fundamental requirement, as stipulated in Article 3-A of Decree-Law No. 198/2012, of 24 August. Each document series (e.g., sales invoices, credit notes, invoice-receipts) must have a unique validation code.
• Sequential number: Corresponds to the position of the document within its respective series. For example, "1/12345" means it is document number 12345 of series "1".

The practical and non-negotiable rule is that no document series can be used without its prior communication to the AT. Creating a new series in invoicing software without proper registration on the Tax Portal is one of the most common and, at the same time, most costly errors, potentially leading to high penalties. It is essential that taxpayers, or their accountants, ensure that all series in use are duly communicated and validated by the AT before the first document is issued.

QR Code: The Digital Bridge in Tax Documents

The Quick Response Code (QR Code) became mandatory in Portugal from 01/01/2022, in accordance with Ordinance No. 195/2020, of 13 August, which regulates the provisions of Article 29, No. 4, of Decree-Law No. 28/2019. Its scope is vast, extending not only to invoices but to all fiscally relevant documents, including transport documents, receipts, and conference documents.

The main function of the QR Code is to facilitate the communication of invoice elements to the AT by end consumers. By scanning the code with a smartphone, consumers can verify the authenticity and compliance of the document, as well as report any irregularities. For companies using certified invoicing software, the generation of the QR Code is automatic and integrated into the issuance process. However, problems can arise in situations of customised print templates, where the QR Code may be inadvertently cut, shrunk, or omitted, especially in duplicate copies or document copies. It is crucial to verify the integrity of the QR Code on all issued documents to avoid non-conformities.

Monthly SAF-T: Electronic Invoicing Communication

The communication of invoice elements to the AT, through the SAF-T (Standard Audit File for Tax purposes) invoicing file or via webservice, is a monthly obligation with a strict deadline. This communication must be made by the 5th day of the following month after the documents are issued (Article 3 of Decree-Law No. 198/2012, of 24 August). It is important to note that the old deadline, which allowed communication until the 8th day, has not been in force since 2023.

Occasional tolerances for the submission of monthly SAF-T are exceptional and only occur by governmental dispatch, as was the case for the December 2025 SAF-T, whose communication was accepted without penalty until 09/01/2026. Taxpayers should not, however, count on these exceptions. Non-communication or communication outside the deadline implies the application of penalties, in accordance with Article 117, No. 9 of the General Regime of Tax Infractions (RGIT).

The following table summarises the main obligations and deadlines in force in 2026:

Certified Invoicing Software: Obligation and Criteria

The use of certified invoicing software is a cornerstone of the modern tax system, aiming to ensure the integrity, authenticity, and legibility of issued documents. The mandatory nature of this certification is established by various legal norms, namely Article 123, Nos. 8 and 9 of the Corporate Income Tax Code (CIRC), Article 4 of Decree-Law No. 28/2019, of 15 February, and Ordinance No. 363/2010, of 23 June.

Certification is mandatory for taxpayers who meet any one of the following criteria:

• Turnover exceeding €50,000 in the previous year. This is the most common and comprehensive criterion. For example, a company that invoiced €55,000 in 2025 is obliged to use certified software in 2026.
• Use of invoicing software, regardless of turnover. If a company, even with a turnover below €50,000, chooses to use a computer program to issue invoices, that program must be certified by the AT.
• Organised accounting. Companies that, by legal imposition or their own choice, adopt the organised accounting regime are obliged to use certified invoicing software.
• Since 01/07/2021: Non-residents with VAT registration in Portugal. This measure aims to ensure the compliance of foreign entities operating in the Portuguese market and subject to VAT.

It is important to clarify that the €100,000 threshold, sometimes cited in some sources, corresponds to the old wording of Ordinance No. 363/2010, which was superseded by Decree-Law No. 28/2019. The currently applicable limit is €50,000.

Software certification ensures that it meets specific technical requirements, such as the impossibility of altering records, the creation of compliant SAF-T files, and the correct generation of ATCUD and the QR Code. The use of non-certified software, when mandatory, is a serious infraction subject to a penalty.

Common Errors to Avoid and Their Respective Penalties

The complexity of tax rules and constant technological evolution can lead to errors that, although sometimes involuntary, have serious financial consequences. The AT has been intensifying supervision, and digitalisation allows it to detect non-conformities more easily. Here are 5 common errors that generate penalties:

1. Uncommunicated series: The creation of new document series (e.g., at the beginning of a new year, for a new store, or for credit notes) without prior registration on the Tax Portal leads to the issuance of documents with an invalid ATCUD. The penalty for lack or delay in communicating series, framed in Article 117, No. 9 of the RGIT, can range from €200 to €10,000.
2. SAF-T after the 5th day: Relying on the old deadline (8th day) or "combining two months" of communication is a serious error. The deadline is unequivocally the 5th day of the following month. Each communication outside the deadline is a separate infraction. For example, if a company communicates the SAF-T for January and February in March, it will be subject to two penalties, each potentially between €200 and €10,000.
3. Invoicing in Excel or Word when certified software is mandatory: For companies exceeding a turnover of €50,000, using any invoicing software, or having organised accounting, issuing invoices in programs like Excel or Word constitutes the use of non-certified software. This infraction is punishable by penalties ranging from €1,500 to €18,750, in accordance with Article 128, No. 2 of the RGIT.
4. Mutilated or illegible QR Code: The use of customised print templates that cut the QR Code, make it illegible, or omit it, especially in duplicates, prevents its reading by consumers and the AT. Although the law does not specify a direct penalty for an illegible QR Code, non-compliance can be framed as an infraction of Article 123, No. 8 of the CIRC, which requires the issuance of documents under conditions that allow their verification, or Article 128, No. 3 of the RGIT, for using non-compliant software, with penalties between €1,500 and €18,750.
5. "Forgotten" documents: The mandatory nature of ATCUD and the QR Code is not limited only to invoices. Transport guides, receipts, and conference documents also require the presence of these elements. Omission in any of these documents constitutes an infraction similar to that of invoices, with potential application of penalties between €200 and €10,000, under Article 117, No. 9 of the RGIT.

Penalties in Summary

Penalties for non-compliance with invoicing obligations are significant and aim to discourage non-compliance. It is essential that companies are aware of the risks associated with each infraction.

To illustrate the financial impact, consider a small company that failed to communicate its monthly SAF-T for three months and, additionally, used non-certified software when its turnover exceeded €50,000. This company could face:

• 3 penalties for delayed SAF-T communication: 3 x €200 (minimum value) = €600.
• 1 penalty for using non-certified software: €1,500 (minimum value).
• Minimum total penalties = €2,100.

This amount can quickly escalate to tens of thousands of euros if the maximum penalty values are applied or if there is recidivism.

Frequently Asked Questions about Invoicing in 2026

To consolidate information and answer the most common questions, we present a set of relevant questions and answers for invoicing in 2026.

What is ATCUD?

ATCUD is the Unique Document Code, mandatory since 01/01/2023. It consists of the series validation code (assigned by the AT after prior communication) and the sequential number of the document within that series. Its purpose is to uniquely identify each fiscally relevant document.

Is the QR Code mandatory on all documents?

Yes, the QR Code has been mandatory since 01/01/2022 on all invoices, transport documents, receipts, and conference documents, in accordance with Ordinance No. 195/2020. Its presence is essential for consumers to verify the authenticity of documents.

What is the deadline for monthly SAF-T?

The invoicing SAF-T must be communicated to the AT by the 5th day of the month following the issuance of the documents. Non-compliance with this deadline entails penalties ranging from €200 to €10,000, according to Article 117, No. 9 of the RGIT.

Who needs certified software?

The use of certified invoicing software is mandatory for taxpayers with a turnover exceeding €50,000 in the previous year, for those who use invoicing software regardless of turnover, for those with organised accounting, and for non-residents with VAT registration in Portugal (since 01/07/2021).

Is Accounting SAF-T already mandatory?

No, the mandatory nature of Accounting SAF-T was postponed by the State Budget for 2026. It will be applicable to periods of 2027, with submission scheduled only for 2028 within the scope of IES (Simplified Business Information).

Can I use manual invoices?

The issuance of manual invoices is permitted only in exceptional situations, such as computer system failure, and must be followed by data recovery in the certified software as soon as possible. However, even manual invoices must comply with invoicing requirements, including the indication of ATCUD, if applicable, and communication to the AT.

What is the importance of a certified accountant in these obligations?

A certified accountant plays a fundamental role in ensuring tax compliance. From communicating ATCUD series, to supervising the issuance of documents with the correct QR Code, and timely submission of monthly SAF-T, the CC ensures that the company complies with all obligations, minimising the risk of penalties and optimising processes. In HVR accounting plans (available from €150/month — see prices), SAF-T communication and ATCUD series management are the responsibility of the firm, relieving the taxpayer of this concern.

Practical Recommendations and Conclusion

The invoicing landscape in Portugal in 2026 is one of increasing digitalisation and rigour. Compliance with ATCUD, QR Code, and SAF-T requirements is not just a legal obligation, but an imperative for the sustainability and credibility of any business. Preventing errors and adopting good practices are the best defence against heavy penalties and tax complications.

To ensure compliance, we recommend:

• Regular Audit: Conduct periodic internal audits of invoicing processes to identify and correct potential failures before they become tax problems.
• Continuous Training: Ensure that all personnel involved in issuing tax documents are properly trained and updated on the latest legal requirements.
• Partnership with Certified Software: Keep invoicing software always updated and certified, ensuring that it complies with all AT technical specifications.
• Professional Support: Rely on the support of an experienced certified accountant. This professional not only ensures the correct application of norms but can also offer strategic advice to optimise the company's tax processes.

The digitalisation of invoicing is an irreversible reality that, if well managed, can bring significant efficiencies to companies. However, it requires constant attention and a commitment to compliance. Do not let the complexity of these obligations become an obstacle to your business. Invest in compliance and ensure a peaceful tax future for your company.

For a free diagnosis of your company's tax compliance or to find out how HVR Business Consulting can help manage your invoicing and accounting obligations, contact us today.

Sources and Legal References

• Decree-Law No. 28/2019, of 15 February: Establishes measures to combat tax fraud and evasion, related to transacted goods and services, and amends the VAT Code, the IRC Code, the IMI Code, the Sisa and Inheritance Tax Code, the Stamp Duty Code, the General Regime of Tax Infractions and the Complementary Regime of Tax and Customs Inspection Procedure.
• Decree-Law No. 198/2012, of 24 August: Creates a new regime for the communication of invoices and other fiscally relevant documents, and amends the VAT Code, the IRC Code and the General Regime of Tax Infractions.
• Ordinance No. 195/2020, of 13 August: Regulates the provisions of No. 4 of Article 29 of Decree-Law No. 28/2019, of 15 February, regarding the requirements for invoicing programs and the mandatory nature of the QR Code and ATCUD.
• Ordinance No. 363/2010, of 23 June: Regulates the requirements for invoicing programs and the conditions for their use.
• Dispatch No. 351/2021-XXII of the SEAF, of 22 October 2021: Postponement of the mandatory nature of ATCUD.
• Corporate Income Tax Code (CIRC), Article 123, Nos. 8 and 9: Rules relating to invoicing and invoicing programs.
• General Regime of Tax Infractions (RGIT), Articles 117, No. 9 and 128, Nos. 2 and 3: Penalties applicable to infractions related to invoicing and invoicing programs.
• State Budget for 2026 (relevant provisions on the postponement of Accounting SAF-T).