ATCUD (Código Único de Documento — Unique Document Code) is a code that has been mandatory on tax documents issued in Portugal since 2022, unambiguously identifying each invoice, receipt, transport document or similar. ATCUD is made up of the document series validation code (obtained from the Tax Authority) and the document's sequential number, separated by a hyphen.
The ATCUD requirement, together with the QR Code that also became mandatory, increases the traceability of invoicing in Portugal and reduces tax fraud. Technically, it requires the invoicing software to be integrated with the Tax Portal to obtain series validation codes and to issue them correctly on every document.
MULTI and MAXIRETAIL by INFOS issue ATCUD to the standard, integrated with the Tax Authority, with automatic series management. For customers with multiple companies or parallel series (frequent in groups), the system handles the complexity without manual intervention.