BT-43Seller contact email address
Official rule text
[BR-DE-28] BT-43 shall contain exactly one @ character, which shall not be flanked by a space or a dot, but by at least two characters on each side. A dot should not appear at the beginning or at the end.
Official text (German): In 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. Ein Punkt sollte nicht am Anfang oder am Ende stehen.
Why this error occurs
XRechnung checks the format of the seller contact e-mail address (BT-43): exactly one @, at least two characters on each side of it, no space or dot directly next to the @, and no dot at the beginning or end. The rule matches cbc:ElectronicMail in the seller cac:Contact (UBL) or ram:EmailURIUniversalCommunication/ram:URIID (CII) against a regular expression. Typical failures are display names ("Billing <billing@x.de>"), a mailto: prefix, two addresses separated by comma or semicolon, trailing spaces or dots, or placeholders like "-".
How to fix it
Write one plain e-mail address only, e.g. invoice@muster-gmbh.de, without display name, angle brackets, mailto: or trailing punctuation. Trim whitespace in the export. If several mailboxes exist, pick the one that is monitored for invoice queries. This is a warning, but a malformed address means rejection notices never arrive.
Example (valid)
<cbc:ElectronicMail>invoice@muster-gmbh.de</cbc:ElectronicMail>What the validator checks
Checked element (context):
UBL
/ubl:Invoice/cac:AccountingSupplierParty/cac:Party/cac:Contact | /cn:CreditNote/cac:AccountingSupplierParty/cac:Party/cac:ContactTest (XPath):
matches(normalize-space(cbc:ElectronicMail), $XR-EMAIL-REGEX)CII
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeAgreement/ram:SellerTradeParty/ram:DefinedTradeContactTest (XPath):
matches(normalize-space(ram:EmailURIUniversalCommunication/ram:URIID), $XR-EMAIL-REGEX)Check your invoice
Drop your XML or PDF on the validator and every failed rule is linked to its page here. Free, no account, the file is not stored.
Same check via API:
curl -F file=@invoice.xml https://einvoicechecker.com/v1/validateRelated rules
BR-DE-7Seller contact email address (BT-43) is missingBR-DE-1Payment instructions (BG-16) are missingBR-DE-2Seller contact (BG-6) is missingBR-DE-3Seller city (BT-37) is missingBR-DE-4The element "Seller post code" must be transmittedBR-DE-5Seller contact point (BT-41) is missingBR-DE-6Seller contact telephone number (BT-42) is missingBR-DE-8The element "Buyer city" must be transmitted
Frequently asked questions
What does BR-DE-28 mean?
BR-DE-28 is a xrechnung rule: BT-43 shall contain exactly one @ character, which shall not be flanked by a space or a dot, but by at least two characters on each side. A dot should not appear at the beginning or at the end.
Will my invoice be rejected because of BR-DE-28?
No. BR-DE-28 is a warning: the invoice is accepted but the recipient sees the notice. Fix it anyway, warnings often become errors in later rule versions.
Which formats does BR-DE-28 apply to?
XRechnung in UBL or CII syntax, including ZUGFeRD / Factur-X PDFs with the XRECHNUNG profile. Invoices to German public authorities (federal, state and municipal) must pass it. Syntax: UBL and CII.
Source: XRechnung 3.0.2, schematron 2.6.0 (KoSIT, September 2026). Catalogue generated from the official schematron on 2026-10-14.