# BT-157 Item Standard Identifier

A standard identifier for the item, such as a GTIN.

## Quick answer

A standard identifier for the item, such as a GTIN.

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

- validate
- convert

## In plain language

A standard identifier for the item, such as a GTIN.

A standard identifier for the item, such as a GTIN.

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

## What you usually enter here

Standard item identifier

Typical valid values include: 4006381333931

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

- 4006381333931

## Related Fields

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

- [BT-158 Item Standard Identifier Scheme](/resources/xrechnung/bt-158-item-standard-identifier-scheme)

## 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-157

### Data Type:
identifier

### Cardinality:
0..1

### Requirement:
Optional

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:InvoiceLine/cac:Item/cac:StandardItemIdentification/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)