iXBRL tagging links visible UK accounts text and numbers to FRC taxonomy concepts. The tagging should start from the final accounts, use accounting meaning rather than label matching only, and be validated before HMRC or Companies House filing.
This guide is source-linked to official HMRC, Companies House and FRC material where available. Check current official guidance before treating the filing route, deadline or taxonomy choice as final.
Start from controlled accounts
Tagging should start only when the accounts version is controlled enough for review. Late changes to accounts can invalidate previous mapping and validation evidence.
- Lock or version the source accounts.
- Record whether the accounts are draft, approved or signed.
- Retag and revalidate after material changes.
Tag by meaning
Good iXBRL tagging connects the disclosure to the correct accounting concept. The label printed in the accounts may not exactly match the taxonomy concept name.
- Review context and accounting policy.
- Check signs, periods, units and dimensions.
- Escalate judgemental mappings.
Review before filing
Before HMRC or Companies House submission, the reviewer should check validation output, material tags and submission evidence.
- Resolve blocking errors.
- Assess warnings and quality issues.
- Retain final tagged file and validation report.
Common risks
Common risks include treating HMRC and Companies House as one combined filing, using an old taxonomy assumption, copying prior-year tags without review, ignoring validation warnings, missing separate deadlines and losing evidence of approval.
- Do not rely only on prior-year files.
- Do not treat validation as a substitute for accounting or tax review.
- Escalate unusual balances, late filings or regulator-specific issues early.
Evidence to retain
The filing record should show the source accounts used, the HMRC or Companies House route decision, mapping or tagging review, validation results, corrections, approvals and final filing confirmation.
- Save signed or approved accounts and version details.
- Save validation and correction evidence for iXBRL files.
- Save HMRC, Companies House, upload or adviser handoff confirmation.
Before you rely on this route
- Source accounts version controlled.
- FRC taxonomy selected.
- Material tags reviewed.
- Validation report saved.
- Final submission evidence retained.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
Companies House accounts filing is separate from HMRC Company Tax Return filing. UK companies should confirm the accounts deadline, prepare statutory accounts under the applicable accounting framework, and keep evidence of the Companies House filing as well as any HMRC iXBRL submission.
Are HMRC and Companies House filings the same?
No. Companies House accounts filing and HMRC Company Tax Return filing are separate UK obligations, even where the same statutory accounts support both workflows.
Can prior-year iXBRL files be reused?
Prior-year files can be a reference, but the current company facts, accounts, taxonomy, validation rules and official filing route should be checked again.
When should professional review be used?
Use professional review when the route is unclear, the filing is late, source documents changed, CT600 or tax computations changed, or the entity has unusual disclosures.
This article is general UK iXBRL filing information, not legal, tax, accounting or regulatory advice. Check current HMRC, Companies House and FRC guidance, and seek professional advice before making filing decisions.