# BR-42 Invoice line allowance reason or reason code is required

Each Invoice line allowance (BG-27) shall have an Invoice line allowance reason (BT-139) or an Invoice line allowance reason code (BT-140).

## Problem Description

> **ERROR**: EN 16931 core business rule (CEN)

## Context and Significance

This is an EN 16931 core rule and the line-level counterpart of BR-33. Each line allowance needs a reason so the buyer can check it, for example damaged packaging or a promotional price. The error appears when an ERP exports only the line discount amount without a reason text or UNCL5189 code; provide at least one. If both are given, BR-CO-07 requires that they describe the same reason.

## Solution

Add cbc:AllowanceChargeReason text or cbc:AllowanceChargeReasonCode (UNCL5189) to the line allowance; if both are given they must describe the same reason.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-42)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-42)

## Valid Examples

- BT-139 = "Damaged packaging"
- BT-140 = 95 (discount)

## Invalid Examples

- Line allowance with amount only, no reason or reason code

## Code Examples

### Valid XML
```
<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>
  <cbc:AllowanceChargeReason>Damaged packaging</cbc:AllowanceChargeReason>
  <cbc:Amount currencyID="EUR">3.00</cbc:Amount>
</cac:AllowanceCharge>
```

### Invalid XML
```
<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:Amount currencyID="EUR">3.00</cbc:Amount>
</cac:AllowanceCharge>
```

## Affected Fields

- [BT-139 Invoice line allowance reason](/resources/xrechnung/bt-139-invoice-line-allowance-reason)
- [BT-140 Invoice line allowance reason code](/resources/xrechnung/bt-140-invoice-line-allowance-reason-code)

## Related Rules

- [BR-41](/resources/kosit-validator-errors/br-41-line-allowance-amount-required)
- [BR-CO-07](/resources/kosit-validator-errors/br-co-07-line-allowance-reason-code-match)

## Validation Tools

- [Official KoSIT Validator](https://github.com/itplr-kosit/validator): Run the official KoSIT validator with the XRechnung configuration to check EN 16931 and XRechnung rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Find validation errors during conversion and review each correction.

## Related Resources

- [Official Specification](https://docs.peppol.eu/poacc/billing/3.0/rules/ubl-tc434/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [All validation errors](/resources/kosit-validator-errors): Overview of the EN 16931, XRechnung and Peppol validation rules explained here.