# Document reference

Link from an invoice to another document (order, contract, prior invoice).

## Definition

Link from an invoice to another document (order, contract, prior invoice).

## Explanation

Improves traceability and automation in accounts payable.

Often required in public procurement contexts.

## Related resources

- [XRechnung fields](/resources/xrechnung)

## Related terms

- [Credit note](/resources/glossary/credit-note): Document that reduces or cancels a previously issued invoice amount.
- [Purchase order (PO)](/resources/glossary/purchase-order): Buyer-issued document ordering goods/services, often referenced by an invoice.
- [Contract reference](/resources/glossary/contract): Identifier linking an invoice to a contract or framework agreement.