Byte Order Mark (BOM) at file start

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

What is a BOM

A Byte Order Mark is a 2- or 3-byte signature at the very start of a text file that signals which Unicode encoding the file uses:

Encoding	BOM bytes
UTF-8	`EF BB BF`
UTF-16 BE	`FE FF`
UTF-16 LE	`FF FE`

Why AT rejects BOMs

Windows-1252 has no BOM concept. The official SAF-T schema and AT's intake parser expect the first byte of the file to be the < of the XML prolog, not a Unicode signature.

When a BOM is present, the XML declaration parses but the file is rejected at intake without a useful error.

How a BOM gets there

Saving from Notepad on Windows ("UTF-8 with BOM" is the default).
Some ERPs prepend a BOM when exporting Unicode-aware XML.
Manual file conversion through a tool that adds a signature.

How to fix

Remove the leading 2 or 3 bytes. The XML body otherwise stays unchanged.

# Linux/macOS one-liner for UTF-8 BOM
sed -i '1s/^\xEF\xBB\xBF//' my.xml

SAFTCheck strips the BOM automatically when you click "Auto-fix and download".

Detecting a BOM

Open the file in a hex editor. The first three bytes should be 3C 3F 78 (i.e. <?x), not EF BB BF.

XML encoding declaration (Windows-1252) — the broader encoding requirement.