# BR-01

> The invoice is missing its Specification identifier (BT-24). This is the cbc:CustomizationID that declares which rule set the invoice follows; add it with the Peppol BIS Billing 3.0 value.

Checked against Peppol BIS Billing 3.0 2026.5

Canonical: https://einvoicecheck.eu/rules/br-01

## Official rule text

An Invoice shall have a Specification identifier (BT-24).

## Why did my invoice fail BR-01?

The invoice must carry a Specification identifier (BT-24), which declares the CIUS or extension the document conforms to (e.g. the Peppol BIS Billing 3.0 or EN 16931 customization ID). Validators and receivers use this value to select the correct rule set for processing. In UBL it is carried in cbc:CustomizationID at the document root.

## Common causes

- cbc:CustomizationID element is missing entirely from the invoice root.
- The element is present but empty or whitespace-only.
- A custom or misspelled specification URN is used that the receiver does not recognise.
- The value was placed in ProfileID instead of CustomizationID.

## How do I fix it?

```
<cbc:CustomizationID>urn:cen.eu:en16931:2017#compliant#urn:fdc:peppol.eu:2017:poacc:billing:3.0</cbc:CustomizationID>
```