A specialized tool for generating ZUGFeRD 2.1 and Factur-X compliant electronic invoices with support for visible multi-page PDF merging.
Install & Download
1. ClawHub CLI
The fastest way to install a skill directly from the registry.
npx clawhub@latest install zugferd-invoice
2. Manual Installation
Copy the skill folder to one of these locations
~/.openclaw/skills/ <project>/skills/ Priority: Workspace > Local > Bundled
3. Prompt Installation
Copy this prompt to OpenClaw to install it automatically.
Help me install zugferd-invoice using Clawhub. If Clawhub is not installed, install it first (npm i -g clawhub).
Prefer to download?
Get the raw skill files in a ZIP archive.
What is zugferd-invoice?
The zugferd-invoice skill is a technical solution designed for developers and businesses needing to comply with German and European e-invoicing mandates. It enables the creation of ZUGFeRD 2.1 and Factur-X compliant documents, which are essential for B2B and government transactions. By utilizing Openclaw Skills, users can automate the complex process of embedding machine-readable XML into human-readable PDF/A-3b files.
This skill stands out by offering a unique workflow that merges supplemental documents, such as time reports or expense logs, directly into the visible pages of the invoice PDF. This ensures that the final document is both legally compliant under EN16931 standards and easy for human recipients to review. By leveraging open-source powerhouses like MustangProject and GhostScript, this skill provides a robust alternative to expensive, proprietary invoicing APIs.
zugferd-invoice Use Cases
- Generating ZUGFeRD 2.1 compliant e-invoices for German B2B and public sector (Leitweg-ID) requirements.
- Merging multiple PDF documents into a single, visible multi-page invoice while maintaining PDF/A-3b compliance.
- Automating Factur-X electronic invoice generation for the French market using Openclaw Skills.
- Validating existing PDF invoices to ensure they meet the EN16931 technical specifications for electronic data exchange.
How zugferd-invoice Works
- The skill first extracts the ZUGFeRD XML metadata from the source e-invoice to preserve technical data.
- It uses GhostScript to merge the primary invoice PDF with any secondary attachments into a unified, multi-page document.
- The merged document is then converted to the strict PDF/A-3b format to meet archiving and compliance standards.
- Using the MustangProject library, the previously extracted XML is embedded back into the merged PDF structure.
- A final validation check is performed to confirm the output is a valid ZUGFeRD document ready for submission.
zugferd-invoice Setup
To get started with this skill, first install the necessary system dependencies:
brew install openjdk@21 ghostscript
Next, download the MustangProject JAR file into the appropriate directory:
mkdir -p ~/.openclaw/tools/mustang
curl -L https://github.com/ZUGFeRD/mustangproject/releases/download/core-2.22.0/mustang.jar -o ~/.openclaw/tools/mustang/mustang.jar
Ensure Java is in your path and run the Openclaw Skills workflow via Python:
export PATH="/opt/homebrew/opt/openjdk@21/bin:$PATH"
python3 scripts/zugferd_pages_workflow.py --invoice Rechnung.pdf --attachment Zeitnachweis.pdf --output Rechnung_komplett.pdf
zugferd-invoice Data Schema & Taxonomy
The skill manages invoice data through a structured input/output workflow. It ensures that both visual elements and metadata are preserved.
| Data Element | Type | Description |
|---|---|---|
| Invoice PDF | Input | The primary PDF/A-3 invoice containing original ZUGFeRD XML. |
| Attachment | Input | Additional PDF files (e.g., reports) to be merged or attached. |
| Output PDF | Output | A validated, multi-page PDF/A-3b file with embedded XML metadata. |
| XML Schema | Metadata | Follows ZUGFeRD 2.1 / Factur-X (EN16931) specifications. |
zugferd-invoice Advanced Features
- Visible Page Merging: Unlike standard tools that only attach files, this Openclaw Skills utility makes attachments visible as additional pages.
- Fallback Attachment Workflow: Includes a secondary mode for cases where source PDFs have incompatible ICC profiles, ensuring files are still embedded as attachments.
- Automated Validation: Integrated MustangProject validation to provide immediate feedback on PDF/A and ZUGFeRD compliance status.
- No-API Dependency: Fully self-hosted and open-source logic, eliminating reliance on external paid billing services.
SKILL.md
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