# BT-156 Buyer Item Identifier

An identifier assigned by the buyer to the item.

## Quick answer

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

- [Validate XML](/en/xrechnung-validator?source=resource&bt=BT-156)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&bt=BT-156)

## In plain language

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.

## Where the field sits

BT-156 belongs to the Lines part of the invoice. UBL 2.1 Syntax: Invoice › cac:InvoiceLine › cac:Item › cac:BuyersItemIdentification › cbc:ID. CII (UN/CEFACT) Syntax: rsm:CrossIndustryInvoice › rsm:SupplyChainTradeTransaction › ram:IncludedSupplyChainTradeLineItem › ram:SpecifiedTradeProduct › ram:BuyerAssignedID.

## Valid Examples

- BUYER-SKU-42

## Related Fields

- [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

## XML Implementation

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

### CII (UN/CEFACT) Syntax
```
/rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:IncludedSupplyChainTradeLineItem/ram:SpecifiedTradeProduct/ram:BuyerAssignedID
```

## 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)