ATCUD explained: what the code on Portuguese invoices and delivery notes means

ATCUD stands for Código Único de Documento — unique document code. According to the AT, it is formed by the validation code of the series, assigned by the AT, and the sequential number of the document within that series. The result identifies the document uniquely, whatever its issuer, type and series.

It is printed on the document next to a QR code. Both come from the same legal requirement: Decreto-Lei 28/2019 requires invoices and other fiscally relevant documents to include a QR code and a unique document code, in the terms set by ministerial order; Portaria 195/2020 of 13 August sets those terms.

The ATCUD became mandatory on 1 January 2023; during 2022 it was optional. For transport documents, the goods-in-circulation regime (Decreto-Lei 147/2003, art. 5) also requires the sender to include the unique document code when it communicates the guia to the AT before the transport.

• Invoices (faturas) and simplified invoices
• Credit notes and debit notes
• Transport documents: guia de remessa, guia de transporte and equivalents
• Receipts and other fiscally relevant documents

1. 01The issuer defines its document series — for example, one series of invoices and one of guias per billing system.
2. 02Before using a series, the issuer communicates it to the AT, which returns a validation code for that series.
3. 03Each document in the series is numbered sequentially. The law requires numbering to be progressive and continuous within each series, for a period not shorter than a tax year.
4. 04On the document, the ATCUD typically appears as the series validation code, a hyphen and the document’s sequential number.

The receiver has no obligation relating to the ATCUD — it does not report or validate anything. But for anyone checking supplier documents, a code that is unique per document is useful:

• Duplicate detection. The same invoice arriving by email and on paper, or a guia photographed twice by two people on site, carries the same ATCUD. Combined with the supplier, it is a clean key to catch it.
• One delivery record per load. When a supplier sometimes sends goods with a fatura and sometimes with a guia, the codes help keep one record per delivery. See guia de transporte vs guia de remessa vs fatura.
• Clear references in disputes. Quoting the ATCUD of a guia or invoice when you ask for a credit note removes ambiguity about which document you mean.

Audiree is built in Portugal and works with Portuguese construction companies. When AI reads a guia or a fatura, it captures the document number and ATCUD, and uses them with the supplier to detect duplicates before anything is approved. The document then goes through the line-level checks against the contract — see common supplier invoice discrepancies.

To be precise about limits: Audiree does not validate the ATCUD, the QR code or signatures with the AT, and does not issue documents. The ATCUD is used as a duplicate key, nothing more.