# BT-14 Sales order reference

Reference to the seller-side sales order behind the invoice.

## Quick answer

Reference to the seller-side sales order behind the invoice.

> **Invoice basics**: Core document identifiers, dates, process identifiers, and high-level invoice context.

## In plain language

Reference to the seller-side sales order behind the invoice.

Reference to the seller-side sales order behind the invoice.

This helps the seller, buyer, and ERP systems reconcile the invoice against the internal order process.

## What you usually enter here

Internal sales order identifier

Typical valid values include: SO-88421

Optional according to EN 16931-1.

## What goes wrong often

Avoid values like: , AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Examples in context

This helps the seller, buyer, and ERP systems reconcile the invoice against the internal order process.

Optional according to EN 16931-1.

## Valid Examples

- SO-88421

## Invalid Examples

- AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Related Fields

This helps the seller, buyer, and ERP systems reconcile the invoice against the internal order process.

- [BT-13 Purchase Order Reference](/resources/xrechnung/bt-13-purchase-order-reference)

## 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-14

### Data Type:
text

### Cardinality:
0..1

### Requirement:
Optional

### Max Length:
50 characters

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:OrderReference/cbc:SalesOrderID
```

### CII (UN/CEFACT) Syntax
```
/CrossIndustryInvoice/SupplyChainTradeTransaction/ApplicableHeaderTradeAgreement/ram:SellerOrderReferencedDocument/ram:IssuerAssignedID
```

## Why the standard cares about this field

### Business Context
This helps the seller, buyer, and ERP systems reconcile the invoice against the internal order process.

### Legal Requirement
Optional according to EN 16931-1.

## 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)