Portugal certified invoicing, ATCUD and SAF-T (PT)

What certified invoicing in Portugal is

Certified invoicing in Portugal means issuing invoices only from a software program and version that the Tax and Customs Authority (AT) has certified, which signs every document, stamps it with an ATCUD code and a QR code, and reports it to the AT. It matters because the certification belongs to the software, not to the business, so choosing a program is itself a compliance decision.

The rules sit mainly in Decree-Law 28/2019, which consolidated invoicing and record-keeping obligations and was amended by Decree-Law 48/2020 and Decree-Law 49/2025, and in Ordinance 363/2010 on software certification. Around them sit the monthly invoice communication, the SAF-T (PT) audit file and, for public contracts, structured e-invoicing. This guide explains each piece as of September 2026.

Who must use AT-certified invoicing software

Under article 4 of Decree-Law 28/2019, taxpayers established in Portugal must use exclusively software that has received prior AT certification whenever any one of the first three conditions below applies. In practice this reaches almost every company and a large share of sole traders.

If the certified program fails, invoices must be issued on pre-printed forms from an authorised printer and later recovered into the program. Since 1 July 2025, Decree-Law 49/2025 has also let taxpayers use the AT's own invoicing applications instead, and requires them for a person carrying out a single taxable operation.

• Turnover above EUR 50,000 in the previous calendar year, or an annualised figure above it in the first year
• Use of any invoicing software at all: if you invoice from a computer program, it must be certified
• An obligation to keep organised accounts (contabilidade organizada), or an election to do so
• Cash registers and other electronic means only for simplified invoices under article 40 of the VAT Code
• A public list of certified programs and versions, with their producers, kept by the AT

How certification works: it belongs to the program

The software producer, not the user, applies for certification by submitting a Model 24 declaration with its public key, and must meet the technical requirements set by the AT's Order 8632/2014. Each certificate covers a named program and version; a new major version, or a program built in-house, needs its own certification.

A certified program signs every invoice with the producer's private RSA key. The signature covers the document's key data and the signature of the previous document in the same series, forming a chain, so an altered or deleted document breaks every signature after it. Four characters of the signature and the certificate number are printed on the document, for example Processado por programa certificado n.º 1234/AT.

The AT can and does cancel certificates. When a program's certificate is withdrawn, its users must move to another certified program, so check the AT list before you sign a contract and keep an eye on it afterwards.

• Documents cannot be deleted; a cancelled document stays in the database marked as cancelled
• Numbering is sequential and continuous within each series for at least a fiscal year
• Training-mode documents must say so and remain stored
• The program must export a valid SAF-T (PT) invoicing file on request

ATCUD, document series and the QR code

Before a document series is used, the business, usually through its software, communicates the series to the AT, which returns a validation code for it. The ATCUD, the unique document code, is that validation code followed by a hyphen and the document's sequential number, for example ATCUD:JJ37MMKQ-35 for invoice 35 of that series.

Every invoice and other fiscally relevant document must also carry a two-dimensional QR code containing the issuer's and buyer's tax numbers, the document type, date, ATCUD, the VAT breakdown by rate and region, totals and the signature characters. The technical rules are in Ordinance 195/2020. The QR code became mandatory from 1 January 2022 and the ATCUD from 1 January 2023, after earlier postponements.

A certified program cannot offer an option to omit the QR code. Because the series must exist at the AT before its first document, opening a new branch, till or document type is a small compliance task, not just a settings change.

• Communicate each series to the AT before its first use
• ATCUD = series validation code, hyphen, sequential number
• QR code on paper and PDF invoices, generated by the certified program
• Separate series for invoices (FT), simplified invoices (FS), invoice-receipts (FR), credit notes (NC) and debit notes (ND)

Monthly communication of invoices to the AT

Separately from issuing, the elements of every invoice must be communicated to the AT. Under Decree-Law 198/2012 this can be done in real time through a web service or by uploading a SAF-T (PT) invoicing file on the Portal das Finanças. Since 1 January 2023 the deadline has been the 5th day of the month after the invoice was issued.

The communication feeds the e-fatura system, where buyers see invoices issued with their tax number and where the AT cross-checks VAT returns. A business with no invoices in a month must say so. Errors found after the deadline are corrected by communicating the corrected data, not by editing the original invoice.

• Real-time web service or monthly SAF-T (PT) upload
• Deadline: the 5th of the following month
• A declaration of no invoicing when nothing was issued
• Credit notes communicated with a reference to the invoice they correct

SAF-T (PT): the invoicing file and the accounting file

SAF-T (PT) is Portugal's standard audit file for tax purposes, an XML file defined by Ordinance 321-A/2007 and currently in version 1.04_01 under Ordinance 302/2016. Businesses with a commercial, industrial or agricultural main activity that keep computerised accounts, and all users of certified invoicing software, must be able to produce it when the tax inspection asks.

There are two views of the same structure. The invoicing SAF-T contains master data and commercial documents and is the file used for the monthly communication. The accounting SAF-T contains the chart of accounts and journal movements and is meant to accompany the annual Simplified Business Information return (IES). Decree-Law 48/2020 set the rules for that submission, including the masking of descriptions and personal data with a key supplied by the national mint and press (INCM) and a ban on the AT using the detailed data outside an inspection.

The mandatory submission of the accounting SAF-T with the IES has been postponed several times. As of September 2026, the legislated calendar points to the IES for the 2026 period, filed in 2027. Confirm the date on the Portal das Finanças before you plan, and make sure your accounting program can generate and mask the file.

• Invoicing SAF-T: customers, products, taxes and documents; used monthly
• Accounting SAF-T: chart of accounts and journal entries; linked to the IES
• Current structure: version 1.04_01, Ordinance 302/2016
• Accounting file masking through an INCM key before submission

Worked example: invoice, credit note and postings

A Lisbon wholesaler issues invoice FT 2026/35 on 8 September 2026 from its certified program: goods EUR 1,000 plus VAT at the mainland standard rate of 23 percent, EUR 230, total EUR 1,230. The printed invoice shows ATCUD:JJ37MMKQ-35, the QR code, four signature characters and the program's certificate number. Under the Portuguese accounting standards system (SNC) the posting is Dr 211 Customers 1,230 / Cr 711 Sales of goods 1,000 / Cr 2433 VAT charged 230.

On 22 September the customer returns goods worth EUR 200. The wholesaler issues credit note NC 2026/4, referring to FT 2026/35: 200 plus 46 VAT, 246 in total, with its own ATCUD from the NC series. It posts Dr 717 Sales returns 200 / Dr 2433 VAT charged 46 / Cr 211 Customers 246, leaving EUR 984 receivable. Both documents are communicated to the AT by 5 October.

If the invoice had carried a wrong price, the wholesaler could not edit it: the certified program would only allow a credit note, or cancellation with the document kept as cancelled. That is exactly what the signature chain enforces.

E-invoicing in Portugal: B2B and public contracts

Portugal separates certified invoicing, which is mandatory, from structured e-invoicing, which is mandatory only for public contracts. As of September 2026 there is no general obligation to exchange structured XML invoices between businesses; B2B invoices may be on paper, in PDF or in another electronic format by agreement, provided they come from certified software with ATCUD and QR code.

An electronic invoice needs guaranteed authenticity and integrity, which article 12 of Decree-Law 28/2019 links to a qualified electronic signature or seal, or to EDI. A transitional regime allowed plain PDF invoices to count as electronic invoices; according to the European Commission's country page, from 1 January 2026 a PDF invoice sent as an electronic invoice must carry a qualified electronic signature or seal. That tolerance has been extended before, so confirm the current position on the Portal das Finanças.

• B2G: structured e-invoices in the CIUS-PT format of EN 16931, in UBL 2.1 or GS1 XML
• Large companies: mandatory for public contracts since 2021
• Small, medium-sized and micro enterprises: the B2G start date was postponed several times; confirm the current date with eSPap
• B2B: no structured e-invoicing mandate as of September 2026
• From 1 July 2030: EN 16931 e-invoices for intra-EU B2B supplies under ViDA

Archiving invoices and records

Books, records and supporting documents must be kept in good order for ten years under article 19 of Decree-Law 28/2019, or longer where a right exercised by the taxpayer runs longer. Invoices issued and received electronically must be kept unchanged, in chronological order and only in electronic form.

Backup copies of electronic archives are compulsory and must be stored in a different place from the originals. A scanned folder with no link to the ledger meets neither the letter nor the purpose of these rules; the audit trail has to run from the goods or service to the document and to the posting.

• Ten-year retention for books, records and supporting documents
• Electronic invoices kept only electronically and unaltered
• Backups stored separately from the originals
• Documented management controls that create a reliable audit trail

What an accounting system must do in Portugal

Portugal splits obligations between the invoicing program and the accounting program. Check both halves, and the link between them, against this list.

• Issue invoices only from a program and version on the AT's certified list
• Communicate series and print ATCUD and QR code on every document
• Report invoices to the AT in real time or by the 5th of the following month
• Export a valid SAF-T (PT) invoicing file on request
• Generate the accounting SAF-T and mask it with the INCM key for the IES
• Correct only by credit or debit notes; never delete a document
• Use the SNC chart of accounts, or map to it, for statutory reporting
• Keep ten years of records with separate backups

Portuguese compliance and Skyline Nexus ERP

AT certification is granted to a specific program and version, so the question to ask any vendor is whether its exact version appears on the AT's public list. Certification of Skyline Nexus ERP for Portugal, with ATCUD, QR code and SAF-T (PT) exports, is part of our market-by-market roll-out; tell us that you trade in Portugal and we will confirm your go-live date. Until it appears on the AT list, invoices to Portuguese customers should be issued from an AT-certified program or the AT's own invoicing applications.

The workable route in the meantime is to keep issuing in the certified program and bring the sales into Skyline Nexus ERP with the Import Sales tool, which has a preview and can revert an import batch, so stock, customer balances and the general ledger stay complete. Skyline Nexus then provides the ledger disciplines: invoice numbering per location, centrally maintained tax rates and tax groups, posted journals corrected by reversal, fiscal periods that can be locked, and an Accounting Audit Trail. Skyline Nexus ERP runs in English and Arabic, with interface translations for Portuguese among many other languages.