A UK iXBRL audit trail should show the source accounts, taxonomy version, mapping decisions, validation results, corrections, reviewer approvals and final HMRC or Companies House submission evidence. It should allow the filing pack to be reconstructed later.
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.
Source evidence
Keep the exact accounts version used for tagging, plus CT600 and computation versions where the HMRC route applies.
- Save approved or signed accounts.
- Save CT600 and tax computations where relevant.
- Record version dates and preparer/reviewer names.
Tagging evidence
The audit trail should show taxonomy selection, material mapping decisions, extensions and corrections.
- Record FRC taxonomy version.
- Save mapping or tagging review notes.
- Document extension concepts and why they were used.
Submission evidence
Separate evidence should be retained for HMRC and Companies House where both filings apply.
- Save final validation report.
- Save HMRC acknowledgement.
- Save Companies House confirmation separately.
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 documents saved.
- Taxonomy and mapping evidence saved.
- Validation results saved.
- Reviewer approval saved.
- Submission confirmations saved.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
iXBRL Audit Trail Requirements depends on the UK filing route, entity profile and source records. Confirm whether the issue relates to HMRC Company Tax Return filing, Companies House accounts filing, FRC taxonomy tagging, or a combination before 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.