How Inline XBRL works
An Inline XBRL report is an XHTML page. Wherever a number or statement appears, a tag that the reader never sees links it to a concept in the taxonomy, along with the reporting entity, the period and the unit.
When software opens the file it pulls out those tagged facts as a standard XBRL dataset, ready to validate and compare. When a person opens it, they see the formatted report exactly as the company published it.
XBRL vs iXBRL
Both carry the same tagged facts and pass the same taxonomy checks. The difference is what travels with them.
Who requires Inline XBRL
Inline XBRL is now the default for document-style filings. The US SEC requires it of all filers. In the UK, more than two million companies file iXBRL each year with HMRC and Companies House. ESMA uses it as the basis of the European Single Electronic Format for listed companies’ IFRS annual financial reports, and Japan’s Financial Services Agency and Denmark’s business register use it too (XBRL International).
Since 2023, a growing number of securities regulators have required XBRL tagging of sustainability disclosures as well.
When a supervisor should choose it
Ask whether the report is mainly a document or mainly data. If supervisors, investors or the public read it as a document, Inline XBRL keeps one authoritative version. If it is a high-volume prudential return read by systems first, traditional XBRL or xBRL-CSV is usually the better fit. Many programmes use both.
Where AI fits, and where people decide
Tagging is the part of Inline XBRL that preparers find most costly. AI can suggest tags as the report is drafted and explain a failed check in plain language. On the supervisory side, it can read the narrative sections alongside the tagged numbers and point out where they disagree.
The preparer still signs off every tag, and deterministic validation still decides whether a filing passes. AI speeds up the work. It does not take responsibility for the result.
- 1Sort your reports into documents and data, and mandate iXBRL only for the documents.
- 2Publish the taxonomy and a short list of required tags well before the first deadline.
- 3Set a clear policy on extension concepts, or comparability across filers suffers.
- 4Give filers a free validator with plain-language messages before launch.
- 5Plan how supervisors will use the extracted facts from the first cycle, not the third.
Where Line4 fits
Line4 is a SupTech platform for financial regulators. It collects returns in XBRL, Excel and CSV, validates them against your taxonomies and rules at the point of submission, and puts AI to work reading them, with supervisors making every decision. If you work with a standard we have not yet run in production, we will say so plainly and show you how we would approach it.
Questions
What is iXBRL?
Inline XBRL (iXBRL) is an open standard from XBRL International that embeds XBRL tags in a human-readable XHTML document, so one file can be read by people and processed by machines.
What is the difference between XBRL and iXBRL?
Traditional XBRL is a machine-readable data file. Inline XBRL embeds the same tagged facts inside a readable document. Both are validated against the same taxonomy and produce the same data.
Who requires Inline XBRL?
The US SEC requires it of all filers. In the UK, more than two million companies file iXBRL each year with HMRC and Companies House. ESMA requires it for listed companies’ IFRS annual financial reports under ESEF, and Japan and Denmark use it too.
Should a regulator use iXBRL or XBRL for supervisory returns?
Use Inline XBRL for reports that people read as documents, such as annual accounts. Use traditional XBRL or xBRL-CSV for template-heavy prudential returns that systems process first.
Can AI tag Inline XBRL?
AI can suggest tags and explain validation failures, which cuts preparation time. The preparer should still approve every tag, and deterministic validation rules should decide whether the filing passes.