## TL;DR

Peppol BIS Billing 3.0 validation errors come as Schematron rule failures with codes like PEPPOL-EN16931-R001; each code names the exact business rule violated (missing seller ID, bad tax category, totals mismatch). Read the validation report, map each failed assertion to its rule description, and fix the data at the source: most failures are missing identifiers, wrong tax category codes, or totals that do not foot. Validate locally with the same Schematron rules before sending so failures never reach the network. Keep a runbook of your top ten rule failures with the fix for each.

## The query

```text
Peppol BIS Billing 3.0 validation errors on e-invoices: how to read them
```

## Use this when

- Peppol e-invoices failing validation
- Decoding PEPPOL-EN16931 rule failures
- Pre-send validation for Peppol invoices

## Not for

- Access point or SMP lookup errors (transport layer)
- Envelope or signature errors (different validation stage)

## Steps

1. Pull the full validation report with all failed assertions.
   Expected output: You have the complete failure list, not just the first.
2. Map each rule code to its business rule description.
   Expected output: Each failure is understood, not just numbered.
3. Fix the data at the source: identifiers, tax categories, totals.
   Expected output: The invoice is corrected where the data lives.
4. Re-validate locally with the official Schematron before resending.
   Expected output: The invoice passes before it hits the network.
5. Add the failure to your top-ten runbook with the exact fix.
   Expected output: Repeat failures get faster each time.

## Variant phrasings

### Peppol BIS Billing 3.0 validation error

### PEPPOL-EN16931 rule failed

### how to read Peppol validation report

## Root cause

BIS Billing 3.0 layers EN 16931 business rules over UBL syntax: the XML can be perfectly formed and still fail because a business rule (totals must foot, tax category must be valid) is violated. Reading the rule, not the XML, is the skill.

## Edge cases

- Different Peppol authorities add country-specific rules on top; validate against the right ruleset
- Totals rounding: PEPPOL rules are strict about line vs document total arithmetic

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_QRFvevA-NdQ3aaC4o92-Eg