# BT-25 Preceding invoice reference

Reference to an earlier invoice that this invoice corrects, supplements, or continues.

## Quick answer

Reference to an earlier invoice that this invoice corrects, supplements, or continues.

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

## In plain language

Reference to an earlier invoice that this invoice corrects, supplements, or continues.

Reference to an earlier invoice that this invoice corrects, supplements, or continues.

This field is important for credit notes, corrections, and chains of invoices such as partial or final invoicing.

## What you usually enter here

Referenced invoice number

Typical valid values include: INV-2025-991

Optional according to EN 16931-1, but required by the business scenario when the invoice refers back to another invoice.

## What goes wrong often

Avoid values like: , AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Examples in context

This field is important for credit notes, corrections, and chains of invoices such as partial or final invoicing.

Optional according to EN 16931-1, but required by the business scenario when the invoice refers back to another invoice.

## Valid Examples

- INV-2025-991

## Invalid Examples

- AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Related Fields

This field is important for credit notes, corrections, and chains of invoices such as partial or final invoicing.

- [BT-26 Preceding invoice issue date](/resources/xrechnung/bt-26-preceding-invoice-issue-date)
- [BT-3 Invoice Type Code](/resources/xrechnung/bt-3-invoice-type-code)

## 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-25

### Data Type:
text

### Cardinality:
0..1

### Requirement:
Optional

### Max Length:
50 characters

### Since Version:
Optional

## XML Implementation

### UBL 2.1 Syntax
```
/Invoice/cac:BillingReference/cac:InvoiceDocumentReference/cbc:ID
```

### CII (UN/CEFACT) Syntax
```
/CrossIndustryInvoice/SupplyChainTradeTransaction/ApplicableHeaderTradeSettlement/ram:InvoiceReferencedDocument/ram:IssuerAssignedID
```

## Why the standard cares about this field

### Business Context
This field is important for credit notes, corrections, and chains of invoices such as partial or final invoicing.

### Legal Requirement
Optional according to EN 16931-1, but required by the business scenario when the invoice refers back to another invoice.

## 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)