A UK iXBRL pre-filing checklist should confirm the final accounts version, CT600 and computations where relevant, FRC taxonomy version, material tag review, validation results, approvals and separate HMRC or Companies House submission evidence.
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 file checks
Pre-filing validation starts with the source material. The accounts, CT600 and computations should be aligned before technical validation is treated as final.
- Confirm final accounts version.
- Confirm CT600 and computation version where relevant.
- Confirm Companies House filing version separately.
Tagging and validation checks
Review the taxonomy, material tags, contexts, signs and validation report before releasing the file.
- Check selected FRC taxonomy version.
- Review material tags and extensions.
- Resolve blocking validation errors and assess warnings.
Approval and evidence checks
Before submission, the pack should show who reviewed the iXBRL file and where the filing acknowledgement will be stored.
- Record reviewer approval.
- Save validation output.
- Save HMRC or Companies House acknowledgement after filing.
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
- Final accounts controlled.
- CT600/computations aligned if relevant.
- Taxonomy version recorded.
- Validation output clean or explained.
- Approval and acknowledgement retained.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
iXBRL Pre-filing Validation Checklist 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.