BR-DE-28In BT-43 soll genau ein @-Zeichen enthalten sein, welches nicht von einem Leerzeichen, einem Punkt, aber mindestens zwei Zeichen auf beiden Seiten flankiert werden soll.
Official rule text
Ein Punkt sollte nicht am Anfang oder am Ende stehen.
The seller contact email address (BT-43) should be plausibly formed: exactly one @, no whitespace, and a dot in the domain. The rule text asks for more than the expression tests, and it reports only a warning either way.
- Severity
- Warning
- Applies to
- CII, UBL
- Rule set
- v2026-08-31
- Checked on
Written and checked against the official KoSIT rule set by Dmytro Yalanskyi, NormAPI.
Why does BR-DE-28 happen?
Placeholders like "-" or "none", two addresses in one field ("a@firma.de; b@firma.de"), or a truncated value ending in a dot. The rule text sounds stricter than the check is: it wants two characters either side of the @, no dot beside it and none at the start. The expression ^[^@\s]+@([^@.\s]+\.)+[^@.\s]+$ enforces only part of that — a@b.c with a single character on the left passes, and so do a.@b.c and .@b.c. What does fail reliably: a missing @, two @, whitespace in the value, a domain without a dot, and a trailing dot.
What the validator checks
The expression the official KoSIT rule set evaluates — not paraphrased, but read from the Schematron file it ships. UBL and CII address different document trees, so the same rule reads differently in each.
- UBL
matches(normalize-space(cbc:ElectronicMail), $XR-EMAIL-REGEX)Variables in it
- $XR-EMAIL-REGEX
- '^[^@\s]+@([^@.\s]+\.)+[^@.\s]+$'
- CII
matches(normalize-space(ram:EmailURIUniversalCommunication/ram:URIID), $XR-EMAIL-REGEX)Variables in it
- $XR-EMAIL-REGEX
- '^[^@\s]+@([^@.\s]+\.)+[^@.\s]+$'
Source: rule set v2026-08-31
How do you fix BR-DE-28?
Enter exactly one valid address, e.g. invoices@company.com (cac:Contact/cbc:ElectronicMail in UBL, ram:EmailURIUniversalCommunication/ram:URIID in CII). Multiple recipients do not belong in the field — use a shared mailbox instead.
In the XML
A UBL fragment. The CII path is named above — same change, different element names.
<cac:Contact>
<cbc:ElectronicMail>rechnung@muster.de, buchhaltung@muster.de</cbc:ElectronicMail>
</cac:Contact><cac:Contact>
<cbc:ElectronicMail>rechnung@muster.de</cbc:ElectronicMail>
</cac:Contact>Related rules
NormAPI provides technical validation, not tax or legal advice.