BR-DE-28
Seller Contact Email Has an Invalid Format (BT-43)
What This Error Means
BR-DE-28 checks the syntax of the seller contact email (BT-43). According to the KoSIT text it should contain exactly one @, not flanked by a space or a dot, with at least two characters on each side, and no dot at the start or end. The current KoSIT configuration (31 August 2026) checks it with the regular expression ^[^@\s]+@([^@.\s]+\.)+[^@.\s]+$: no whitespace anywhere, exactly one @, and a domain made of at least two non-empty parts separated by dots. Umlauts are accepted; older configurations (for example 31 October 2024) used a stricter ASCII-only pattern and flagged them. The rule is a warning. It also fires, together with BR-DE-7, when cac:Contact exists but cbc:ElectronicMail is empty.
How to Fix It
Enter exactly one address without spaces in cac:Contact/cbc:ElectronicMail, for example rechnung@muster.de. Addresses like 'a@muster.de; b@muster.de' (two addresses, space) or 'rechnung@muster' (no dot in the domain) trigger the warning. With an older validator configuration, also avoid umlauts, for example by using the ASCII (Punycode) form of the domain.
<cac:Contact> <cbc:Name>Buchhaltung</cbc:Name> <cbc:Telephone>+49 30 1234567</cbc:Telephone> <cbc:ElectronicMail>rechnung@muster.de</cbc:ElectronicMail> </cac:Contact>
Fix Automatically
Upload your invoice to our Smart Repair engine. It checks the file against the full KoSIT rule set, including BR-DE-28, and corrects supported fields with a GoBD audit trail.
Open Smart RepairRelated Errors
Other commonly encountered validation errors