UK iXBRL requirements depend on the filing route. HMRC CT600 filing focuses on the Company Tax Return, tax computations and tagged accounts where required; Companies House filing focuses on statutory accounts. The FRC taxonomy choice and validation evidence should be checked before submission.
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.
Two filing routes to separate
Most confusion comes from treating HMRC and Companies House as one combined filing. Build the checklist around two routes: the HMRC Company Tax Return pack and the Companies House statutory accounts filing.
- HMRC route: CT600, Corporation Tax, computations and iXBRL evidence.
- Companies House route: statutory accounts and accounts filing evidence.
- Some workflows may use the same accounts source, but the obligations remain separate.
Taxonomy and tagging requirement
The iXBRL requirement is a tagging and validation control, not just a file format change. The tagged data should reflect accounting meaning, current taxonomy selection and the final approved accounts.
- Confirm UK GAAP or IFRS taxonomy assumptions.
- Map using accounting meaning rather than label text only.
- Revalidate after any account, computation or tag correction.
Evidence requirement
The filing pack should make it easy to reconstruct what was filed, why that route applied and who reviewed the final version.
- Retain source accounts and version history.
- Retain validation reports and correction notes.
- Retain HMRC and Companies House filing confirmations 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
- HMRC and Companies House routes are documented separately.
- Approved accounts and tax computations are controlled.
- FRC taxonomy route is recorded.
- Validation results are retained.
- Submission confirmations are saved.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
UK iXBRL Filing 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.