How do I fix PEPPOL-EN16931-R080?

Review your Invoice XML structure and correct the issue described by this rule. Check relevant cbc: and cac: elements per EN 16931 (PEPPOL-EN16931-R080). You can also use Invoice Navigator's compliance engine to correct this automatically in your pipeline.

Is PEPPOL-EN16931-R080 a critical error?

Yes, PEPPOL-EN16931-R080 is a critical error that will cause invoice rejection. It must be fixed before submission.

Can PEPPOL-EN16931-R080 be automatically fixed?

Many instances of PEPPOL-EN16931-R080 can be automatically corrected using Invoice Navigator's compliance engine. The fix is applied in your pipeline with full audit evidence.

Which accounting software causes PEPPOL-EN16931-R080?

PEPPOL-EN16931-R080 is commonly seen in exports from All invoicing software. These packages sometimes generate invoices that need adjustment.

errorEN 16931

`PEPPOL-EN16931-R080`:Too many project references

The invoice has more than one project reference at the document level. Peppol allows only a single project reference per invoice. If your invoice relates to multiple projects, use only the primary one at the document level.

Severity

Fatal

Rule set

EN 16931

Country

All EU

Fix type

BLOCKED

Engine Classification

Financial or legal field · Modification blocked by policy

What is PEPPOL-EN16931-R080?

PEPPOL-EN16931-R080 is a fatal validation rule defined in the EN 16931 specification. It validates the XPath: cac:ProjectReference — Peppol rule PEPPOL-EN16931-R080. Only one ProjectReference element is allowed at document level. element in the UBL invoice XML.

When this rule fires, the invoice is non-compliant and will be rejected by Peppol access points and national validation services. The sending system receives a rejection response and the invoice does not reach the buyer.

Target path: XPath: cac:ProjectReference — Peppol rule PEPPOL-EN16931-R080. Only one ProjectReference element is allowed at document level.

This error requires manual correction — financial fields are protected by policy.Test This Error ↓

Why This Error Matters

Invoice will be rejected by PEPPOL validation. Document level supports only one project reference.

PEPPOL-EN16931-R080 is a hard failure. Invoices that trigger this rule are rejected at the access point and never reach the recipient. In Peppol networks, this means your sending system receives an MLR (Message Level Response) with a rejection status. The invoice must be corrected and re-sent, adding delay to your payment cycle.

Validator Behavior

·Causes invoice rejection
·Error returned: PEPPOL-EN16931-R080
·Specification: EN 16931

How to Fix It

Review the project references

Your invoice has multiple ProjectReference elements. Check which one is the primary project for this invoice.

Keep one reference

Remove the extra ProjectReference elements, keeping only the primary one.

Move to line level

If items belong to different projects, consider using line-level references instead of document-level.

Before / After

Failing XML

<Invoice>
  <!-- Issue: Only one project reference is allowed on document level. -->
</Invoice>

Corrected XML

<Invoice>
  <!-- Issue resolved per EN 16931 -->
</Invoice>

Technical Reference

XPath

XPath: cac:ProjectReference — Peppol rule PEPPOL-EN16931-R080. Only one ProjectReference element is allowed at document level.

SpecEN 16931

StrategyCannot automatically determine which project reference to keep — this is a business decision that the invoice issuer must make

Common Causes

·ERP exports both project and sub-project references
·Multiple project IDs added during manual editing
·Template includes placeholder project references

Seeing this in production? The API handles PEPPOL-EN16931-R080 automatically. See the fix response →

Commonly Seen In

All invoicing software

Handle PEPPOL-EN16931-R080 Automatically in Your Pipeline

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

Get API Access View API Documentation

PEPPOL-EN16931-R080:Too many project references