Who Must File in iXBRL in the UK?
Complete guide to UK entities required to file in iXBRL format
All UK limited companies, LLPs above audit thresholds, charitable companies, and listed companies must file in iXBRL format. Comprehensive coverage of entity types, size thresholds, and exemptions under current HMRC and Companies House regulations.
Quick Answer: Who Must File in iXBRL?
All UK limited companies must file in iXBRL format regardless of size or activity. The UK has no exemptions with universal iXBRL requirements.
- All Limited Companies: 2.1M UK companies file Corporation Tax and accounts
- LLPs Above Thresholds: £10.2M turnover, £5.1M assets, or 50 employees
- Charitable Companies: Standard rules plus SORP-specific tags
- Listed Companies: UKSEF annual reports (Premium 2025, Standard 2026)
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Approved Compliant ProviderUK Entity Types Required to File in iXBRL
The UK's iXBRL requirements apply to different entity types with specific thresholds, exemptions, and timelines. Understanding your entity classification is essential for compliance.
All UK limited companies incorporated under the Companies Act 2006 must file their statutory accounts and Corporation Tax returns in iXBRL format, regardless of size, turnover, or activity status.
Statutory Accounts (Companies House)
- Micro-entities: Simplified iXBRL tags
- Small companies: Full iXBRL format
- Medium/Large companies: Detailed tagging
- Quoted companies: ESEF requirements
Corporation Tax Returns (HMRC)
- All companies: CT600 in iXBRL
- Supporting computations in iXBRL
- No paper alternative accepted
- Mandatory since April 2011
Key Exemptions for Limited Companies:
NONE. Unlike many other jurisdictions, the UK has no exemptions for limited companies based on size, dormancy, or activity. Even dormant companies must file dormant company accounts in iXBRL format.
LLPs must file accounts in iXBRL format if they exceed audit thresholds or choose to file full accounts rather than simplified versions.
LLP iXBRL Filing Thresholds (2024/25):
Must exceed 2 of 3 criteria for two consecutive years
LLP Exemptions from iXBRL:
- Small LLPs can file simplified accounts without full iXBRL tagging
- Dormant LLPs may file simplified dormant accounts
- But all LLPs must file tax returns (if applicable) in iXBRL format
Charitable companies must file accounts in iXBRL format following either FRS 102 or the Charities Statement of Recommended Practice (SORP), depending on their size and structure.
Charitable Companies
- Follow standard company iXBRL requirements
- Additional charity-specific tags required
- Must include Statement of Financial Activities (SOFA)
- Charity Commission annual return separate
CIOs (since 2022)
- Income over £1m: Full iXBRL accounts
- Income £250k-£1m: Simplified iXBRL
- Income under £250k: Basic tagging only
- Annual return to Charity Commission
Charity SORP Compliance:
Charitable entities must use specialized iXBRL tags that accommodate charity-specific reporting requirements including restricted funds, designated funds, and endowment reporting under FRS 102 and Charities SORP.
Public companies listed on UK exchanges have additional iXBRL requirements beyond standard statutory accounts, particularly for annual reports under the UK Single Electronic Format (UKSEF).
Listed Company iXBRL Requirements:
Standard Requirements:
- Statutory accounts in iXBRL
- Corporation Tax returns
- Companies House filings
UKSEF Requirements:
- Annual reports in iXBRL
- Financial statements tagging
- Narrative reporting sections
Timeline Implementation:
- Premium Listed: UKSEF mandatory from January 1, 2025
- Standard Listed: UKSEF mandatory from January 1, 2026
- AIM Companies: Voluntary adoption with incentives
Size Thresholds and Classification Criteria
UK entities are classified by size using specific financial thresholds that determine the level of iXBRL tagging required and available exemptions.
Micro-Entities
Simplified iXBRL tagging only
Small Companies
Standard iXBRL tagging required
Medium/Large
Detailed iXBRL + audit requirements
Classification Rules
A company qualifies for a smaller category only if it meets at least 2 of the 3 criteria for the current year AND the preceding financial year. This prevents manipulation through one-off adjustments and ensures consistent classification.
Exemptions and Special Cases
While most UK entities must file in iXBRL, certain exemptions and special provisions apply to specific entity types and circumstances.
Complete Exemptions
Sole Traders & Partnerships
Unincorporated businesses file traditional tax returns (SA100, SA800) unless specifically required by sector regulations.
Overseas Companies
Foreign companies with UK branches may use alternative formats if filing equivalent information in their home jurisdiction.
Certain Investment Vehicles
Some specialized investment structures may qualify for alternative reporting frameworks.
Simplified Filing Options
Dormant Companies
Can file simplified dormant company accounts with minimal iXBRL tagging, but still must use structured format.
Small LLPs
Below audit thresholds can file simplified accounts with reduced iXBRL requirements.
Micro-Entities
Can use simplified micro-entity accounts with reduced tagging requirements but still in iXBRL format.
Special Sector Requirements
Certain regulated sectors have additional or modified iXBRL requirements beyond standard company filing obligations.
Financial Services
Banks, building societies, and insurers have enhanced regulatory reporting requirements with sector-specific iXBRL taxonomies.
Housing Associations
Registered social landlords must file using Housing SORP with specialized iXBRL tags for social housing activities.
Academic Institutions
Universities and colleges follow Education SORP requirements with additional iXBRL tagging for education-specific reporting.
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