CSRD Digital Tagging: The Taxonomy Exists, the Mandate Has Not Switched On, and Neither Fact Helps You Wait

A sustainability team finishes its ESRS statement in November. It exists as a document: a hundred-odd pages of narrative, tables and figures, signed off, laid out, exported to PDF, filed. Everyone involved understands it as writing.

The European rulebook does not understand it as writing. It treats the statement as a set of data points, each one identified by a machine-readable label, sitting inside an electronic file that software can read without a human opening it. The two descriptions of the same artefact are not compatible, and one of them is the legal one.

That difference is the whole subject of this article, because it is arriving on a delayed and slightly confusing schedule.

What the law asks for

The CSRD requires sustainability information to be digitally tagged. The mechanism is not a new one: it runs through the European Single Electronic Format, the regime listed companies already use for annual financial reports, governed by Commission Delegated Regulation (EU) 2019/815. Financial statements are marked up against the IFRS taxonomy. Sustainability statements are to be marked up against an ESRS taxonomy, added to the same regulation.

That taxonomy had to be written first. EFRAG did that work and published the XBRL taxonomy for ESRS Set 1 on 30 August 2024. In practical terms it assigns a label to every data point in the standards, so a number in a statement carries its own definition, unit and context rather than depending on the sentence printed next to it.

The taxonomy exists; the mandate has not switched on

Here is where reporting teams tend to get an inaccurate picture. Publishing a taxonomy does not make tagging compulsory. EFRAG’s own digital reporting page still states the position plainly: digital tagging will not be mandatory for companies until the Commission adopts the XBRL taxonomy as part of the ESEF technical standards, which happens by amending the 2019 regulation.

So a company reading only the directive concludes tagging is required, and a company reading only the implementation status concludes it is not yet an issue. Both are half right, and the second half is the one that produces bad planning.

Why the delay is not a reprieve

A late mandate would be a genuine reprieve if tagging were a formatting exercise you could do at the end. It is not, and the reason is worth being precise about.

Tagging requires that each disclosed value be a discrete, typed item: this number, this data point, this unit, this reporting period, this entity, this consolidation boundary. A statement authored as prose does not contain those items. It contains sentences that happen to have numbers in them, and the numbers usually arrive from a spreadsheet whose lineage nobody has documented.

Turning that into a tagged file means going back through the document, extracting every figure, deciding which taxonomy element it corresponds to, and re-entering it with its context attached. On a first CSRD statement that is a project of weeks, performed by the people who have least time in the reporting calendar, at exactly the point when the auditor is also asking where the numbers came from.

Where the figures already live in a system as structured data, tagging is a step at export. The system knows what each value is, because it had to know in order to store it.

The distinction is not really about software. It is about whether a company’s disclosures are a report with a spreadsheet behind it, or a dataset with a report on the front.

The revised ESRS moved the target

There is a second reason to treat the current lull carefully. On 3 July 2026 the Commission adopted the revised ESRS alongside the new Voluntary Standard for undertakings protected by the value chain cap (Commission Delegated Regulation C(2026) 5011 final; see also Linklaters’ summary of the pair).

The revision changed which data points the standards require. A taxonomy is a description of a standard, so a taxonomy built against the 2023 version of ESRS Set 1 no longer describes the standards a company will report under. That work has to be redone before it can be adopted, which is a reasonable explanation for the delay and a poor argument for ignoring it.

Note also what has not changed: the direction. Every revision of this regime so far has cut the number of data points while keeping the requirement that the surviving ones be machine-readable. Simplification has been about volume, not about form.

The part that outlasts the deadline

The tagging requirement is worth taking seriously even setting aside its legal date, because three other things ask for the same underlying discipline.

Assurance. Limited assurance is easier to give over a data set with provenance than over a document with a spreadsheet somewhere behind it. The auditor’s questions are, in substance, the questions a taxonomy asks: what is this figure, what period does it cover, what entities are in it, where did it come from.

Multi-framework reporting. A group reporting under both ESRS and Japan’s SSBJ is not producing two sets of facts. It is producing two presentations of one set. That only works if the facts exist independently of either presentation.

Comparability, which is the point. The reason the EU wants machine-readable statements is so that supervisors, investors and analysts can read a thousand of them at once. A company whose disclosures are readable only by a person reading a PDF opts itself out of every automated screen its capital providers run.

What to do before the mandate lands

Two things are useful now and do not depend on the timing.

The first is to find out, for each figure in your last sustainability statement, whether it exists anywhere as a stored value with its unit, period and boundary attached, or only inside the document. That inventory is uncomfortable and quick, and it is a fair predictor of how expensive the first tagged filing will be.

The second is to stop treating the statement as the artefact and start treating it as one output of the data behind it. The same numbers have to appear in the assurance file, the investor deck, the group parent’s consolidation, and eventually in a tagged XHTML file. Producing each of those by hand from the previous one is where the errors come from.

If you want a view of where your reporting currently sits, our free CSRD readiness check scores you across seven dimensions in about three minutes.