# BT-124 External Document Location

A URI where the supporting document can be accessed externally.

## Quick answer

A URI where the supporting document can be accessed externally.

> **Taxes and totals**: VAT treatment, tax breakdowns, and document totals that validators check closely.

- validate
- convert

## In plain language

A URI where the supporting document can be accessed externally.

A URI where the supporting document can be accessed externally.

References evidence stored outside the invoice when embedding the document is not appropriate.

## What you usually enter here

Resolvable URI

Typical valid values include: https://example.com/documents/delivery-note-1001.pdf

Optional EN 16931 mechanism for externally referenced supporting documents.

## What goes wrong often

Avoid values like: delivery-note.pdf

## Examples in context

References evidence stored outside the invoice when embedding the document is not appropriate.

Optional EN 16931 mechanism for externally referenced supporting documents.

## Valid Examples

- https://example.com/documents/delivery-note-1001.pdf

## Invalid Examples

- delivery-note.pdf

## Related Fields

References evidence stored outside the invoice when embedding the document is not appropriate.

- [BT-122 Supporting Document Reference](/resources/xrechnung/bt-122-supporting-document-reference)
- [BT-123 Supporting Document Description](/resources/xrechnung/bt-123-supporting-document-description)
- [BT-125 Attached Document](/resources/xrechnung/bt-125-attached-document)

## XML mapping and field facts

Open the technical reference if you need XML paths, validator rule codes, legal wording, or schema-specific mapping details.

### Field ID:
BT-124

### Data Type:
identifier

### Cardinality:
0..1

### Requirement:
Optional

### Since Version:
Optional when a supporting document is referenced externally

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:AdditionalDocumentReference/cac:Attachment/cac:ExternalReference/cbc:URI
```

### CII (UN/CEFACT) Syntax
```
/CrossIndustryInvoice/SupplyChainTradeTransaction/ApplicableHeaderTradeAgreement/ram:AdditionalReferencedDocument/ram:URIID
```

## Why the standard cares about this field

### Business Context
References evidence stored outside the invoice when embedding the document is not appropriate.

### Legal Requirement
Optional EN 16931 mechanism for externally referenced supporting documents.

## Official sources and tools

- [KoSIT Validator](https://erechnungsvalidator.service-bw.de/)
- [Invoice Converter](/pdf-to-xrechnung)
- [XRechnung Standard](https://xeinkauf.de/xrechnung/)
- [Test Suite](https://github.com/itplr-kosit/xrechnung-testsuite)