# BT-11 Project Reference An identifier for a project, contract, or framework agreement that this invoice relates to. Used to link invoices to specific projects for cost tracking, procurement processes, or contract management purposes. ## Quick answer An identifier for a project, contract, or framework agreement that this invoice relates to. Used to link invoices to specific projects for cost tracking, procurement processes, or contract management purposes. > **Invoice basics**: Core document identifiers, dates, process identifiers, and high-level invoice context. ## In plain language An identifier for a project, contract, or framework agreement that this invoice relates to. Used to link invoices to specific projects for cost tracking, procurement processes, or contract management purposes. An identifier for a project, contract, or framework agreement that this invoice relates to. Used to link invoices to specific projects for cost tracking, procurement processes, or contract management purposes. Essential for organizations managing multiple projects or contracts. Enables proper cost allocation, budget tracking, and financial reporting by project. Particularly important in public procurement where projects must be tracked for compliance and audit purposes. ## What you usually enter here Free text with alphanumeric characters, hyphens, and underscores Typical valid values include: PROJECT-2024-001, PROJ-EU-DIGITAL-2024, INFRA-BER-001, IT-MODERNIZATION-2024 Optional according to EN 16931-1. However, may be required by specific procurement regulations or organizational policies for project-based invoicing and cost center allocation. ## What goes wrong often Avoid values like: , AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA, PROJECT WITH/SPECIAL\CHARS, PROJECT|INVALID*CHARS ## Examples in context Essential for organizations managing multiple projects or contracts. Enables proper cost allocation, budget tracking, and financial reporting by project. Particularly important in public procurement where projects must be tracked for compliance and audit purposes. Optional according to EN 16931-1. However, may be required by specific procurement regulations or organizational policies for project-based invoicing and cost center allocation. ## Valid Examples - PROJECT-2024-001 - PROJ-EU-DIGITAL-2024 - INFRA-BER-001 - IT-MODERNIZATION-2024 - BUILD-SCHOOL-MUNICH-23 ## Invalid Examples - AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA - PROJECT WITH/SPECIAL\CHARS - PROJECT|INVALID*CHARS ## Related Fields Essential for organizations managing multiple projects or contracts. Enables proper cost allocation, budget tracking, and financial reporting by project. Particularly important in public procurement where projects must be tracked for compliance and audit purposes. - [BT-10 Buyer Reference](/resources/xrechnung/bt-10-buyer-reference-leitweg-id) - [BT-12 Contract reference](/resources/xrechnung/bt-12-contract-reference) - [BT-13 Purchase Order Reference](/resources/xrechnung/bt-13-purchase-order-reference) - [BT-19 Buyer accounting reference](/resources/xrechnung/bt-19-buyer-accounting-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-11 ### Data Type: text ### Cardinality: 0..1 ### Requirement: Optional ### Max Length: 300 characters ### Since Version: Optional ## XML Implementation ### UBL 2.1 Syntax ``` /Invoice/cac:ProjectReference/cbc:ID ``` ### CII (UN/CEFACT) Syntax ``` /rsm:CrossIndustryInvoice/rsm:SupplyChainTradeTransaction/ram:ApplicableHeaderTradeAgreement/ram:SpecifiedProcuringProject/ram:ID ``` ## Why the standard cares about this field ### Business Context Essential for organizations managing multiple projects or contracts. Enables proper cost allocation, budget tracking, and financial reporting by project. Particularly important in public procurement where projects must be tracked for compliance and audit purposes. ### Legal Requirement Optional according to EN 16931-1. However, may be required by specific procurement regulations or organizational policies for project-based invoicing and cost center allocation. ## FAQ ### When should I use the Project Reference (BT-11)? Use BT-11 when invoicing for work related to a specific project, contract, or framework agreement. This helps the buyer allocate costs correctly and track project expenses. ### How does BT-11 differ from BT-13 (Purchase Order Reference)? BT-11 references the broader project or contract, while BT-13 references the specific purchase order. One project may have multiple purchase orders, but all related invoices share the same project reference. ### Is Project Reference mandatory for German public administration? BT-11 is optional according to EN 16931-1. However, German public authorities may require it for specific procurement projects or framework contracts. Check the tender documents or contract terms. ### Can I use internal project codes as Project Reference? Use the project identifier specified by the buyer or agreed upon in the contract. If no specific format is required, you can use your internal project codes, but ensure they are meaningful to the buyer. ### What happens if I provide both BT-11 and BT-12 (Contract Reference)? Both can be provided when applicable. BT-11 typically references a broader project or program, while BT-12 references the specific contract. Use both when the project spans multiple contracts. ### Are there format requirements for Project Reference in Germany? No specific format is mandated by XRechnung. Use the format specified by the buyer or follow organizational conventions. Common formats include alphanumeric codes with hyphens or underscores. ## 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)