Decoding the CSSF SFDR JSON file: A complete beginner’s guide
In the evolving regulatory landscape of sustainable finance, Luxembourg-based fund managers have faced growing complexity in meeting Sustainable Finance Disclosure Regulation (SFDR) obligations. One of the most significant technical requirements is the CSSF SFDR JSON file; a machine-readable format mandated by the Commission de Surveillance du Secteur Financier (CSSF) for both pre-contractual and periodic disclosures. But what exactly is this JSON file, why does it matter, and how should asset managers prepare?
This guide offers a clear introduction for compliance teams, middle-office professionals, and fund administrators navigating SFDR reporting in Luxembourg.
What is the CSSF SFDR JSON file?
The CSSF JSON file is a structured, machine-readable version of the key sustainability disclosures required under SFDR. It converts the information from Annexes II, III, IV and V, which cover Article 8 and 9 products for both pre-contractual and periodic reporting, into JSON (JavaScript Object Notation) format. It is machine-readable, designed to support automation, validation, and digital submission via CSSF's eDesk platform.
This requirement applies to:
- UCITS and AIFs marketed in Luxembourg,
- Funds categorised as Article 8 or Article 9 under SFDR.
Why did the CSSF introduce JSON format?
While PDF-based disclosures were initially acceptable, they posed challenges in data extraction, supervision, and cross-comparability. The JSON file requirement was introduced to:
- Digitise regulatory filings for better oversight.
- Enable automated validation by the CSSF.
- Ensure standardised and structured sustainability disclosures.
It reflects the broader EU trend of moving toward machine-readable regulatory submissions.
Scope: When and where is it used?
The JSON file must be submitted via the CSSF eDesk portal & should also be accompanied by the PDF if: It is a Periodic report LU non-regulated funds or it is a Pre-Contractual report and a PDF has never been submitted prior.
Key components of the JSON File The structure of the JSON file follows the RTS templates but translated into a nested, tag-based data format. It includes:
• Report Metadata (Header)
• Fund and Sub-fund identifiers
• Sustainability objectives
• Principal Adverse Impacts (PAIs)
• Taxonomy alignment data
• Asset allocation data
• Activities investment share data
• Top 15 Holdings
• Narrative Data
Because JSON is sensitive to syntax, even minor errors (like an extra comma or missing bracket) can lead to rejection during CSSF validation.
How to prepare the JSON file
Step 1: Structure your ESG data
Ensure that all inputs required by Annex II,III,IV or V are structured in a format suitable for JSON conversion (e.g.xlsx). This means standardized metrics, consistent terminology, and validated sources.
Step 2: Use a generator or template tool
There are multiple ways to generate a JSON file:
- Manual editing (not recommended unless very experienced)
- Vendor solutions or RegTech platforms like FE fundinfo
- In-house converters that map templates to JSON schema
Step 3: Validate before submission
The CSSF provides technical specifications and validation schemas. Always test the file through a validator to check for. Professional tools sort this validation fully automatically before the submission takes place:
- Schema compliance
- Syntax errors
- Logical consistency (e.g., date formats, percentage totals)
Challenges and tips for beginners
- Start early: Preparing your JSON file can take longer than expected, especially if source data is fragmented.
- Stay updated: The CSSF may update the schema or requirements. Always work off the latest spec.
- Test extensively: Validate internally before attempting to upload to eDesk.
- Collaborate across teams: Legal, product, ESG, and IT teams must align on content and structure.
What’s next?
With the trend toward structured reporting accelerating, the CSSF JSON file may soon become a blueprint for broader European initiatives. As regulatory expectations rise, asset managers should invest in data governance, automation tools, and cross-functional collaboration to future-proof their ESG reporting capabilities.
Conclusion
The CSSF SFDR JSON file is more than a technical requirement — it's a step toward a more digital, transparent, and comparable ESG reporting framework. For asset managers operating in Luxembourg, mastering this format is essential for compliance and credibility in the sustainable finance arena.
The FE Fundinfo solution allows an easy data ingestion, fully automated production and validation before the actual submission through our Nexus and e-file portals.