# BT-17 Tender or lot reference

Reference to the tender, lot, or procurement package connected to the invoice.

## Quick answer

Reference to the tender, lot, or procurement package connected to the invoice.

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

## In plain language

Reference to the tender, lot, or procurement package connected to the invoice.

Reference to the tender, lot, or procurement package connected to the invoice.

This is especially relevant in public procurement, framework agreements, and project contracts with lot structures.

## What you usually enter here

Tender or lot identifier

Typical valid values include: LOT-04, TENDER-2026-17

Optional according to EN 16931-1.

## What goes wrong often

Avoid values like: , AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Examples in context

This is especially relevant in public procurement, framework agreements, and project contracts with lot structures.

Optional according to EN 16931-1.

## Valid Examples

- LOT-04
- TENDER-2026-17

## Invalid Examples

- AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Related Fields

This is especially relevant in public procurement, framework agreements, and project contracts with lot structures.

- [BT-12 Contract reference](/resources/xrechnung/bt-12-contract-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-17

### Data Type:
text

### Cardinality:
0..1

### Requirement:
Optional

### Max Length:
50 characters

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:OriginatorDocumentReference/cbc:ID
```

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

## Why the standard cares about this field

### Business Context
This is especially relevant in public procurement, framework agreements, and project contracts with lot structures.

### 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)