Validation rule reference

Every rule SAFTCheck applies to your SAF-T (PT) XML, in plain language. Each page covers what AT expects, the most common ways the rule fails, and how to fix it.

encoding.declaration

XML encoding declaration (Windows-1252)

AT requires Windows-1252 encoding. UTF-8 declarations are silently rejected.

encoding.bom

Byte Order Mark (BOM) at file start

AT rejects SAF-T files that start with a UTF-8 or UTF-16 BOM.

nif.mod11

Portuguese NIF — Mod-11 algorithm and prefixes

9-digit Portuguese tax ID; check digit computed via Mod-11 with weights 9..2.

atcud.format

ATCUD format — VALIDATION-SEQUENCE since 2023

Mandatory unique-document code: 8 uppercase alphanumeric chars, dash, sequence ≥ 1.

header.dates

Header dates — StartDate, EndDate, FiscalYear, DateCreated

Time-window invariants AT enforces on the SAF-T Header block.

feature.inline-editor

Inline editor — fix NIF, ATCUD and header dates in place

Edit the offending value next to the finding, re-validate immediately, no ERP round-trip needed.

nif.vies

VIES cross-check — NIF registered in EU VAT exchange

Header NIF is verified against the EU VIES service and the registered name is compared with the SAF-T CompanyName.

Looking for narrative deep dives instead? See the blog for end-to-end fix walkthroughs.