Overview

When sending invoices via PEPPOL through NIZU, certain validations are performed by the PEPPOL network and the recipient’s access point.

If an invoice contains incorrect data, missing information, or fails compliance checks, PEPPOL will return a warning or rejection message.

To make this transparent and actionable, NIZU provides a dedicated tab:

E-Invoices Warnings

This tab is located in the same section where invoices are listed.

It allows users to review, understand, and fix issues quickly.

Where to Find PEPPOL Warnings

1. Go to Invoices

2. Open the tab E-Invoices Warnings

   
   

This section shows all invoices that:

• Were rejected by PEPPOL

• Contain validation errors

• Have compliance warnings

• Could not be delivered to the recipient

Invoices without issues will not appear in this tab.

What You Can See in the Warnings Tab

For each problematic invoice, you can review:

• Invoice number

• Client name

• Date

• Status (Warning / Rejected)

• Detailed PEPPOL error message

• Technical validation feedback (if provided)

This allows you to identify the root cause before correcting and resending.

Common PEPPOL Errors and Issues

Below are the most frequent problems encountered when sending e-invoices.

1. Incorrect Tax Calculation

Cause

• VAT amount does not match the taxable base.

• Rounding differences exceed allowed thresholds.

• VAT percentage does not correspond to the applied tax category.

Example

Subtotal × VAT rate ≠ Declared VAT amount.

Resolution

• Verify line-level VAT calculations.

• Ensure totals match sum of invoice lines.

• Confirm VAT rate matches the correct category.

PEPPOL validation is strict. Even small rounding differences may trigger rejection.

2. Invalid VAT Number

Cause

• Client VAT number is incorrect or malformed.

• VAT number does not match the country code.

• VAT number is no longer active.

• Formatting includes spaces or invalid characters.

Resolution

• Verify VAT number in official registry (e.g., VIES).

• Ensure proper formatting (country code + number).

• Update client data and resend invoice.

3. Client Not Registered in PEPPOL

Cause

The recipient company is not subscribed to the PEPPOL network.

In this case, the invoice cannot be delivered via PEPPOL.

Resolution Options

• Confirm with the client if they are PEPPOL-enabled.

• Request their correct PEPPOL identifier (Participant ID).

• Send invoice via alternative method (PDF/email).

• Wait until client activates PEPPOL.

4. Missing Mandatory Fields

Cause

Required PEPPOL fields are empty or invalid, such as:

• Buyer reference

• Endpoint ID

• Payment terms

• Legal entity information

Resolution

• Complete missing fields in client profile.

• Review invoice metadata.

• Resubmit after correction.

5. Structural Validation Errors

Cause

The invoice does not comply with PEPPOL BIS format rules.

This may include:

• Incorrect document structure

• Unsupported values

• Invalid currency codes

Resolution

These issues are typically resolved by correcting invoice data. If the problem persists, contact support with:

• Invoice number

• Full error message

• Timestamp of submission

Invoice Status Types

Inside the E-Invoices Warnings tab, invoices may show:

• Warning

  Invoice delivered but contains non-blocking compliance alerts.

• Rejected

  Invoice not delivered due to validation failure.

Only rejected invoices require correction and resubmission.

Recommended Workflow

1. Open E-Invoices Warnings

2. Review error details

3. Correct:

   • Client data

   • VAT calculations

   • Missing fields

4. Resend invoice

5. Confirm status changes to Delivered

Important Notes

• PEPPOL validation rules are country-specific and can change.

• Even minor discrepancies in tax calculation may cause rejection.

• NIZU validates data before submission, but final validation is performed by the PEPPOL network.

• Always verify client VAT and PEPPOL registration before sending the first invoice.

Best Practices to Avoid Errors

• Validate VAT numbers at client creation.

• Avoid manual total overrides.

• Keep client legal information complete.

• Confirm PEPPOL participation before issuing electronic invoices.

When to Contact Support

Contact support if:

• The error message is unclear.

• The invoice appears correct but is repeatedly rejected.

• You suspect a network or access point issue.

Provide:

• Invoice number

• Screenshot of error

• Exact PEPPOL message

By centralizing PEPPOL warnings in one place, NIZU ensures that compliance issues are visible, actionable, and traceable — without interrupting your broader invoicing workflow.