# Contract reference

Identifier linking an invoice to a contract or framework agreement.

## Definition

Identifier linking an invoice to a contract or framework agreement.

## Explanation

Frequently required in public sector and large enterprise billing.

Helps compliance, reporting, and dispute resolution.

## Related resources

- [XRechnung guide](/resources/compliance/xrechnung-standard)

## Related terms

- [Document reference](/resources/glossary/document-reference): Link from an invoice to another document (order, contract, prior invoice).
- [Purchase order (PO)](/resources/glossary/purchase-order): Buyer-issued document ordering goods/services, often referenced by an invoice.