# BR-DE-17 Object identifier must be provided

The object identifier must be provided on the invoice.

## Problem Description

The object identifier must be provided on the invoice.

> **ERROR**: XRechnung 3.0

## Context and Significance

Some procurement processes require an invoiced object identifier (for example, an asset, meter, or case identifier) so the receiver can match the invoice to the correct object in their systems.

## Solution

Add the object identifier to the invoice.

## Valid Examples

- OBJECT-12345
- METER-00001234
- ASSET-4711

## Invalid Examples

- Missing object identifier
- Using a description instead of an identifier

## Code Examples

### Valid XML
```
<cac:AdditionalDocumentReference>
  <cbc:ID>OBJECT-12345</cbc:ID>
</cac:AdditionalDocumentReference>
```

### Invalid XML
```
<!-- Missing object identifier reference -->
```

## Technical Details

### Affected Fields
Invoiced Object Identifier

## Related Rules

- [BR-DE-19](/resources/kosit-validator-errors/br-de-19-project-reference-must-be-provided)
- [BR-DE-20](/resources/kosit-validator-errors/br-de-20-contract-reference-must-be-provided)

## Validation Tools

- [Official KoSIT Validator](https://erechnungsvalidator.service-bw.de/): Validate your XRechnung files against all BR-DE rules.
- [Convert PDF to XRechnung](/pdf-to-xrechnung): Automatic validation error fixes when converting.

## Related Resources

- [Official Specification](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)
- [Complete Error List](/resources/kosit-validator-errors): Overview of all German XRechnung validation rules.