Analysis Report
An examination of Annual Financial Report submissions to the FCA's National Storage Mechanism
Under FCA requirements, the iXBRL annual report is the official report of record. According to the FRC's 2023 institutional investor survey, more than 30% of investors are already using XBRL reports for analysis. As AI-driven analysis becomes more prevalent, the quality and availability of structured data becomes increasingly critical for market efficiency and investor protection.
Key facts about the UK's digital reporting regime.
| Mandatory Since | Financial years beginning on or after 1 January 2021 |
| UK Filers | Approximately 930 listed companies |
| Governing Regulation | DTR 4.1.14R-4.1.15R and the onshored ESEF RTS |
| Required Format | XHTML with Inline XBRL tagging for consolidated IFRS financial statements |
| Filing Location | National Storage Mechanism (NSM) |
The FRC's Structured Digital Reporting 2024/25 Insights (April 2025) examined 25 annual reports and identified quality issues including unnecessary custom extensions (~14% of FTSE 100 tags), poor anchoring, incorrect tag semantics, and missing mandatory tags. The FRC has since launched a public UK iXBRL viewer and is using their CODEx project tools for market-wide analysis. This analysis complements that work by examining the broader population of NSM submissions.
All XHTML and HTML files submitted to the NSM during the analysis period, classified by content type and data extractability.
| Category | Count | Percentage | Data Extractable? |
|---|---|---|---|
| Loading data... | |||
1 ESEF iXBRL Package: Complete ESEF-compliant submission with taxonomy package and machine-readable financial data conforming to DTR 4.1.14R requirements.
2 Standalone iXBRL: iXBRL file with extractable XBRL facts but submitted without the full ESEF taxonomy package structure.
3 PDF Conversion: A PDF document converted to HTML/XHTML format (typically via pdf2htmlEX). These preserve visual layout but contain no machine-readable structured data.
4 HTML Announcement: Plain HTML document such as a press release, cover page, or regulatory announcement without XBRL markup.
Based on files with valid iXBRL data.
Distribution of XBRL facts across compliant iXBRL submissions.
| Metric | Value |
|---|---|
| Loading... | |
5 XBRL Facts: Individual tagged data points within an iXBRL document, including numeric values (ix:nonFraction) and textual disclosures (ix:nonNumeric).
6 Taxonomy: The classification schema used to categorise financial data. IFRS-full is the International Financial Reporting Standards taxonomy required for ESEF compliance.
Files grouped by whether structured financial data can be programmatically extracted.
| Status | Count | Percentage |
|---|---|---|
| Loading... | ||
The NSM should provide explicit metadata distinguishing between ESEF iXBRL packages (machine-readable annual reports), PDF conversions (visual representations without structured data), and announcements (press releases and regulatory notifications). This would enable data consumers to filter submissions by type.
Under DTR 4.1.14R and the onshored ESEF RTS, annual financial reports must be submitted in XHTML with valid iXBRL tagging. Consider implementing automated validation at submission time to ensure compliance and reject non-conforming filings.
A small number of submissions include ESEF taxonomy packages but contain no extractable XBRL facts. These require investigation to determine whether they represent malformed submissions or processing errors.
The FRC has launched a public UK iXBRL viewer to promote accessibility of structured annual reports. A complementary NSM filing browser with category filtering would further improve market access to compliant filings, particularly for retail investors and AI-driven analysis tools.
The FRC's Digital Reporting Quality Review identifies issues such as unnecessary custom extensions, poor anchoring, and incorrect tag semantics in otherwise compliant submissions. NSM validation could complement this work by ensuring filings meet basic structural requirements before detailed FRC review.
View individual filings, filter by category, and search by company name or LEI in the interactive data explorer.
Open Data Explorer Read Compliance Primer