# BT-124 External Document Location

A URI where the supporting document can be accessed externally.

## Quick answer

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

- [Validate XML](/en/xrechnung-validator?source=resource&bt=BT-124)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&bt=BT-124)

## In plain language

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.

## Where the field sits

BT-124 belongs to the Attachments part of the invoice. UBL 2.1 Syntax: Invoice › cac:AdditionalDocumentReference[not(cbc:DocumentTypeCode="130")] › cac:Attachment › cac:ExternalReference › cbc:URI. CII (UN/CEFACT) Syntax: rsm:CrossIndustryInvoice › rsm:SupplyChainTradeTransaction › ram:ApplicableHeaderTradeAgreement › ram:AdditionalReferencedDocument[ram:TypeCode="916"] › ram:URIID.

## What goes wrong often

Avoid values like: delivery-note.pdf

## Valid Examples

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

## Invalid Examples

- delivery-note.pdf

## Related Fields

- [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

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:AdditionalDocumentReference[not(cbc:DocumentTypeCode="130")]/cac:Attachment/cac:ExternalReference/cbc:URI
```

### CII (UN/CEFACT) Syntax
```
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeAgreement/ram:AdditionalReferencedDocument[ram:TypeCode="916"]/ram:URIID
```

## Create an XRechnung from your PDF

The converter reads the invoice and shows the fields it found before download, so you can check and correct the values. No PDF? Fill in the XRechnung directly in the form.

- [Convert invoice](/en/pdf-to-xrechnung)
- [Fill in XRechnung in the form](/en/create-xrechnung)

Download requires an account. Subscriptions from €10/month with annual billing (excl. taxes), or €5 per conversion (excl. taxes) without a subscription.

## Official sources and tools

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