# BR-27 Item net price must not be negative

The Item net price (BT-146) shall not be negative; a discounted line still uses a non-negative net price.

## Problem Description

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

## Context and Significance

This is an EN 16931 core rule and a value check, not a presence check. A negative amount on an e-invoice belongs in the quantity or in an allowance, never in the price. The error mainly appears when an ERP exports returns, credit lines or discount lines as items with a negative unit price. Model the discount as a line allowance (BG-27), the return as a negative quantity, and a full reversal as a credit note (381).

## Solution

Set cac:Price/cbc:PriceAmount (CII: ram:NetPriceProductTradePrice/ram:ChargeAmount) to zero or more. Record a discount as an invoice line allowance (BG-27). For a return or credit, use a negative invoiced quantity (BT-129) with a positive price, or issue a credit note.

- [Validate XML](/en/xrechnung-validator?source=resource&rule=BR-27)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&rule=BR-27)

## Valid Examples

- BT-146 = 12.50 — non-negative net price accepted

## Invalid Examples

- BT-146 = -5.00 — negative net price rejected

## Code Examples

### Valid XML
```
<cac:Price>
  <cbc:PriceAmount currencyID="EUR">12.50</cbc:PriceAmount>
</cac:Price>
```

### Invalid XML
```
<cac:Price>
  <cbc:PriceAmount currencyID="EUR">-5.00</cbc:PriceAmount>
</cac:Price>
```

## Affected Fields

- [BT-146 Item net price](/resources/xrechnung/bt-146-item-net-price)

## Related Rules

- [BR-28](/resources/kosit-validator-errors/br-28-item-gross-price-not-negative)

## 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.