# BT-156 Buyer Item Identifier

An identifier assigned by the buyer to the item.

## Quick answer

An identifier assigned by the buyer to the item.

> **Line items**: The goods or services on each invoice line, including quantities, prices, and VAT.

- validate
- convert

## In plain language

An identifier assigned by the buyer to the item.

An identifier assigned by the buyer to the item.

Identifies the invoiced goods or services for buyer, seller, and automated procurement or inventory matching.

## What you usually enter here

Buyer-assigned item identifier

Typical valid values include: BUYER-SKU-42

Defined by EN 16931 for invoice line item identification; mandatory item names and optional identifiers must follow the listed scheme and country code rules.

## What goes wrong often

Avoid values like:

## Examples in context

Identifies the invoiced goods or services for buyer, seller, and automated procurement or inventory matching.

Defined by EN 16931 for invoice line item identification; mandatory item names and optional identifiers must follow the listed scheme and country code rules.

## Valid Examples

- BUYER-SKU-42

## Related Fields

Identifies the invoiced goods or services for buyer, seller, and automated procurement or inventory matching.

- [BT-153 Invoice Line Item Name](/resources/xrechnung/bt-153-invoice-line-item-name)
- [BT-155 Invoice Line Item Seller Identifier](/resources/xrechnung/bt-155-invoice-line-item-sellers-identifier)

## 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-156

### Data Type:
identifier

### Cardinality:
0..1

### Requirement:
Optional

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:InvoiceLine/cac:Item/cac:BuyersItemIdentification/cbc:ID
```

## Why the standard cares about this field

### Business Context
Identifies the invoiced goods or services for buyer, seller, and automated procurement or inventory matching.

### Legal Requirement
Defined by EN 16931 for invoice line item identification; mandatory item names and optional identifiers must follow the listed scheme and country code rules.

## 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)