The digital transformation of sustainability reporting is accelerating, with XBRL tagging and XHTML reporting becoming essential components of compliant corporate communication. In our April webinar, the topic was explored by Kaisa Heikka from CtrlPrint and Jukka Mäkitalo from Granite. Heikka brings extensive experience in financial reporting and the application of digital reporting formats.
XBRL Tagging: Structuring Data for Maximum Impact
XBRL (eXtensible Business Reporting Language) is an international reporting language that allows sustainability data to be tagged into a machine-readable format. This enables automated data usage by authorities, investors, and analysts. More importantly, it is becoming a mandatory element under the CSRD sustainability reporting requirements.
But tagging is not just a technical exercise, it’s also about structuring content meaningfully. “XBRL makes it possible not just to publish information, but to ensure it’s discoverable, interpretable, and comparable,“ Heikka summarises. This allows report users to quickly zero in on what matters most.
In the context of sustainability reporting, tagging focuses on the data points defined by the ESRS standards. It’s the company’s responsibility to ensure that every data element in the report is correctly matched to the corresponding taxonomy point. This process can be streamlined using tools that support multiple taxonomies and allow tagging as part of the regular reporting workflow.
XBRL makes it possible not just to publish information, but to ensure it’s discoverable, interpretable, and comparable
XHTML Reporting: More Than Just a Pretty Document
XHTML is a web-browser-friendly file format that acts as a container for XBRL-tagged reports. In practice, this means a visually familiar report can be opened in a browser, while its underlying structure is machine-readable. The report becomes simultaneously accessible to human readers and processable by digital systems.
According to Heikka, creating an XHTML report involves both format conversion and technical integration of tags. “Simply converting the file to XHTML isn’t enough. You need a separate tool that embeds the tags correctly into the code.”
A fully compliant XHTML report includes metadata such as company identifiers, currency units, reporting periods, and data types. This ensures the information is machine-readable and comparable across European data repositories, such as the forthcoming ESAP system.
Simply converting the file to XHTML isn’t enough. You need a separate tool that embeds the tags correctly into the code.
Ensuring Reliability and Compliance
While directives and standards provide the framework, the practical implementation of reporting falls on companies themselves, including verification. Both the content of the sustainability report and its tagging must be verifiable. “Tag verification is an entirely new area – no one has done it in practice yet,” Heikka points out.
A smooth reporting process depends on clearly defined roles and timelines. Financial departments typically handle the financial statements and management reports, but sustainability data requires cross-departmental collaboration. A technically sound report is only possible when the data, presentation, and tagging are all aligned.
It’s strongly recommended that reports be written following the ESRS structure from the outset. This makes tagging clearer and the final result easier to validate. It also helps readers understand the report’s composition more quickly.
Common Challenges and How to Solve Them
One of the biggest challenges for many organisations is fragmented data. ESG, HR, and financial data are often stored in different systems. No single system can produce publish-ready material on its own. That’s why the reporting process needs a tool that combines data, text, and visuals into a cohesive whole.
Another key issue is managing changes. Reports almost always evolve throughout the process. Numbers and narratives are updated, and multiple stakeholders – from auditors to communications teams – are involved. The tool must therefore support iteration, commenting, and last-minute edits seamlessly.
Thirdly, the timing and legal requirements don’t always align with current reporting practices. Sustainability topics may have previously followed a separate timeline from financial reporting. Now these elements are merging along with a new layer: digital verification.
Where to Begin with Digital Verification?
Start by evaluating your current state: where is the data stored, what’s your reporting schedule, and what kind of software is needed? It’s also crucial to determine how digital reporting can be integrated smoothly into your existing process rather than becoming an extra burden.
Heikka shares her most important lesson from years of experience: “The importance of collaboration cannot be overstated. Without cross-functional cooperation, reporting can easily become siloed and difficult to manage.”
Digital reporting is the future. Talk to our experts and explore Granite’s CSRD tools.
The article was published on 11 April 2025.