How do I fix DE-R-028?

Invalid email format. The seller contact email (BT-43) must contain exactly one @ sign with at least two characters on each side, and no dots at start or end. You can also use Invoice Navigator's compliance engine to correct this automatically in your pipeline.

Is DE-R-028 a critical error?

DE-R-028 is a warning that may not always cause rejection, but indicates a compliance issue.

Can DE-R-028 be automatically fixed?

Many instances of DE-R-028 can be automatically corrected using Invoice Navigator's compliance engine. The fix is applied in your pipeline with full audit evidence.

warningDEUPEPPOL_BIS

`DE-R-028`:Invalid email format. The seller contact email (BT-43) must contain exactly one @ sign with at least two characters on e

Invalid email format. The seller contact email (BT-43) must contain exactly one @ sign with at least two characters on each side, and no dots at start or end.

Severity

Warning

Rule set

PEPPOL_BIS

Country

DEU

Fix type

CONFIRM

Confidence

80%

Engine Classification

Requires user confirmation before application

What is DE-R-028?

DE-R-028 is a warning validation rule defined in the PEPPOL_BIS specification (DEU national rules). It validates the ElectronicMail element under Party > Contact in the UBL invoice XML.

This is a soft validation failure. The invoice may pass initial transmission, but non-compliant values in this field can cause problems during tax audits, buyer-side processing, or downstream VAT reconciliation.

Target path: //cac:AccountingSupplierParty/cac:Party/cac:Contact/cbc:ElectronicMail

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Why This Error Matters

Invoice will be rejected by German XRechnung validators. German e-invoicing has specific format requirements for payment details, contact information, and attachments.

DE-R-028 is a soft failure. The invoice may pass initial validation, but the non-compliant field can cause issues at the receiving end — tax authorities may flag it during audits, buyer ERP systems may fail to process it, or VAT reconciliation may produce mismatches. Fixing warnings before they accumulate prevents larger compliance gaps.

Validator Behavior

·Generates validation warning
·Rejected by PEPPOL Access Points
·Rejected by XRechnung endpoints
·Error returned: DE-R-028
·Specification: PEPPOL_BIS

XML Example

Generic example based on the rule's target XPath. Your actual XML structure may differ.

Before

<!-- Incorrect value -->
<cbc:ElectronicMail>INVALID</cbc:ElectronicMail>

After

<!-- Corrected value -->
<cbc:ElectronicMail>VALID_VALUE</cbc:ElectronicMail>

Technical Reference

XPath//cac:AccountingSupplierParty/cac:Party/cac:Contact/cbc:ElectronicMail

SpecPEPPOL_BIS

Operationset_default

StrategyEnsure seller contact email is present for XRechnung

Common Causes

·Seller email address format invalid
·BT-43 must contain exactly one @ with valid structure
·cbc:ElectronicMail missing @ or has invalid format
·Email has whitespace around @ or invalid characters
·Dot at start/end or adjacent to @ in email address

Seeing this in production? The API handles DE-R-028 automatically. See the fix response →

Last updated: 27 February 2026

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Handle DE-R-028 Automatically in Your Pipeline

The compliance engine auto-remediates this error with controlled safety policies and evidence pack generation.

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DE-R-028:Invalid email format. The seller contact email (BT-43) must contain exactly one @ sign with at least two characters on e