# BT-25 Preceding invoice reference

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

## Quick answer

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

- [Validate XML](/en/xrechnung-validator?source=resource&bt=BT-25)
- [Convert invoice](/en/pdf-to-xrechnung?source=resource&bt=BT-25)

## In plain language

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.

## Where the field sits

BT-25 belongs to the Header part of the invoice. UBL 2.1 Syntax: Invoice › cac:BillingReference › cac:InvoiceDocumentReference › cbc:ID. CII (UN/CEFACT) Syntax: rsm:CrossIndustryInvoice › rsm:SupplyChainTradeTransaction › ram:ApplicableHeaderTradeSettlement › ram:InvoiceReferencedDocument › ram:IssuerAssignedID.

## What goes wrong often

Avoid values like: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Valid Examples

- INV-2025-991

## Invalid Examples

- AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

## Related Fields

- [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

## XML Implementation

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

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

## 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)

Trying it and buying a single conversion work without 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)