Step 1: confirm which taxonomy applies
Before any tagging starts, confirm which framework and taxonomy version governs your report — ESRS XBRL, an ISSB-aligned local taxonomy, or both. See our ESRS vs ISSB comparison if you're not sure which applies, or whether you need both.
Step 2: prepare your source document
Your sustainability statement should be finalised (or very close to final) before tagging begins — tagging an early draft that then changes materially means re-tagging, not just editing tags.
Step 3: map disclosures to taxonomy elements
Each disclosure in your report — a GHG emissions figure, a workforce metric, a governance disclosure — gets mapped to the specific taxonomy element that represents it. This is the most skilled part of the process: getting the mapping wrong (using a similar-sounding but incorrect element) produces a file that validates technically but reports the wrong thing.
Step 4: apply inline tags
Tags are embedded directly into the XHTML version of your report (inline XBRL/iXBRL) — the visual report a reader sees stays the same; the tags are invisible markup underneath that a machine can read.
Step 5: validate
Run the tagged file through validation software to catch structural errors, missing required tags, or taxonomy mismatches before submission — this is what catches most rejection causes before they become a missed-deadline problem.
Step 6: independent review
A second reviewer checks the tagged output against the source report for accuracy — not just technical validity, but whether each tag genuinely represents what it claims to.
In-house, software, or outsourced?
See our ESG software vs ESG reporting service guide for how to think through that specific decision.
Frequently Asked Questions
Can I tag a sustainability statement myself without special software?
Technically some tagging can be done manually, but in practice almost everyone uses either dedicated tagging software or an outsourced service, since manual tagging at scale is error-prone and slow.
Does tagging change how the report looks to a reader?
No — inline XBRL tags are invisible markup embedded in the same XHTML document a person reads normally; the visual report is unchanged.
How long does tagging usually take?
This varies enormously by report length and complexity — a straightforward statement might take days, a complex multi-framework report longer. Get a fixed quote based on your specific scope rather than assuming a standard timeline.