# PEPPOL-EN16931-R121

> Base quantity MUST be a positive number above zero.

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/peppol-en16931-r121

## Official rule text

Base quantity MUST be a positive number above zero.

## Why did my invoice fail PEPPOL-EN16931-R121?

The item price base quantity (BT-149) must be a positive number strictly greater than zero, because it is the denominator that relates the net price (BT-146) to the invoiced quantity. A zero or negative base quantity would make the per-unit price calculation invalid or a division by zero.

## Common causes

- BaseQuantity is set to 0, often from an uninitialised or defaulted field.
- A negative BaseQuantity was produced by a mapping or sign error.
- The element was emitted empty and interpreted as zero by the validator.

## How do I fix it?

```
Provide a positive base quantity: <cbc:BaseQuantity unitCode="C62">1</cbc:BaseQuantity> (never 0 or negative).
```