XBRL (eXtensible Business Reporting Language) is the digital tagging format that makes sustainability data machine-readable. Under the CSRD, all sustainability reports must be tagged in XBRL , transforming narrative PDFs into structured, comparable datasets that regulators, investors, and AI systems can process automatically.
For most companies, XBRL represents a new technical requirement that sits at the intersection of sustainability reporting and digital compliance.
What is XBRL and why does it matter?
XBRL works by assigning standardised tags to individual data points in a report. When a company discloses its Scope 1 emissions, the number receives a specific XBRL taxonomy tag that identifies it unambiguously , regardless of where it appears in the report, what language it is written in, or how the document is formatted.
This matters for three reasons:
Comparability
Investors can compare the climate disclosures of 50,000+ companies across the EU without manually reading each report. Software can extract, aggregate, and benchmark specific datapoints at scale.
Regulatory oversight
National competent authorities and ESMA can monitor compliance programmatically, flagging missing disclosures or outliers automatically.
AI and data services
The machine-readable format feeds directly into ESG rating systems, financial databases, and AI models that analyse corporate sustainability performance.
How XBRL works for CSRD
The CSRD requires companies to submit their sustainability reports in Inline XBRL (iXBRL) format. This is a hybrid approach:
- The report remains a human-readable HTML document , visually identical to a traditional PDF or web report
- Embedded within the HTML are invisible XBRL tags that mark up each datapoint with its taxonomy element
This means a single document serves both purposes: people can read it as a normal report, while machines can extract structured data from the underlying tags.
The ESRS XBRL taxonomy
The taxonomy , maintained by EFRAG and aligned with the European Sustainability Reporting Standards , maps every required disclosure to a specific digital tag. This includes:
- Quantitative datapoints: Scope 1/2/3 emissions, energy consumption, water usage, workforce metrics
- Qualitative disclosures: Policies, governance descriptions, transition plan narratives
- Boolean flags: Whether certain policies or processes exist (yes/no)
- Tables: Breakdown structures for segmented data (by country, by business unit)
The taxonomy contains over 1,100 datapoints, though companies only tag those determined to be material through their double materiality assessment.
Who needs to comply and when?
The XBRL requirement follows the same phased timeline as the CSRD itself:
| Phase | Companies | First report | XBRL required |
|---|---|---|---|
| Phase 1 | Large public-interest entities (already under NFRD) | FY2024 (published 2025) | Yes |
| Phase 2 | All large companies meeting size criteria | FY2025 (published 2026) | Yes |
| Phase 3 | Listed SMEs (with opt-out until 2028) | FY2026 (published 2027) | Yes |
| Phase 4 | Non-EU companies with significant EU activity | FY2028 (published 2029) | Yes |
How to prepare for XBRL tagging
Step 1: Understand your datapoints
Start with your materiality assessment. The XBRL tags you need correspond directly to the ESRS datapoints determined to be material. If a topic is not material, you do not need to tag it.
Step 2: Structure your data
XBRL tagging works best when your underlying data is already structured and clean. This means:
- Consistent units and time periods across disclosures
- Clear mapping between internal data sources and ESRS datapoints
- Documented methodologies that auditors can verify
Step 3: Choose a tagging approach
Companies have three options:
- Internal XBRL team: Build in-house capability using XBRL editing tools. Best for large companies with technical resources.
- Specialised software: Use a sustainability reporting platform that generates XBRL output as part of the reporting workflow.
- External service provider: Outsource tagging to a consultancy. Common for first-year compliance.
Step 4: Validate before submission
XBRL submissions must pass technical validation checks before filing with national registries. This includes taxonomy compliance, calculation consistency, and structural correctness.
Common concerns about XBRL
”We have never done XBRL before”
Many companies already submit financial statements in XBRL under the European Single Electronic Format (ESEF) regulation. The sustainability XBRL builds on the same technical infrastructure.
”It sounds expensive”
The cost depends on your approach. Companies using modern ESG platforms that generate XBRL automatically incur minimal additional cost. Manual tagging by consultancies can be expensive, especially for first-year compliance.
”What about assurance?”
The CSRD requires limited assurance for sustainability reports, including the XBRL-tagged version. Auditors will verify that tags correctly correspond to the reported data.
How Dcycle supports XBRL compliance
Dcycle’s CSRD reporting platform structures your sustainability data around the ESRS taxonomy from the start, making XBRL output a natural byproduct of the reporting process rather than a separate technical exercise.
- Data collection mapped to ESRS datapoints
- Automatic XBRL tag assignment based on your materiality assessment
- Validation checks before export
- Expert advisory on digital filing requirements
Request a demo to see how Dcycle simplifies XBRL compliance.
