To fix UK iXBRL tagging errors, identify whether the issue comes from the source accounts, FRC taxonomy choice, tag selection, context, sign, period or software validation rule. Correct the root cause, revalidate, and keep evidence of the change.
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.
Find the root cause
Start by deciding whether the error is caused by the accounts, the CT600 or computations, the chosen taxonomy, the tag selection, or the technical context used in the iXBRL file.
- Do not change tags blindly to clear an error.
- Compare the tagged fact to the visible accounts.
- Check whether tax computation changes affected the accounts pack.
Correct in the right place
If the source accounts are wrong, correct the accounts workflow. If the source is right but the tag is wrong, correct the taxonomy mapping. If the tag is right but the context is wrong, correct the period, unit or entity context.
- Accounts issue: correct the accounts version.
- Mapping issue: select a better FRC concept.
- Technical issue: fix context, unit, sign or duplicate facts.
Revalidate and document
Every material correction should be followed by a fresh validation run and a reviewer note explaining what changed.
- Save before-and-after validation output where useful.
- Record reviewer approval.
- Keep the final tagged file and submission evidence.
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
- Root cause identified.
- Correction made in source, mapping or context layer.
- Validation rerun completed.
- Reviewer note saved.
- Final file locked for submission.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
UK iXBRL tagging should use the applicable FRC taxonomy and accounting meaning from the source accounts. Teams should avoid label-only matching, validate the tagged file, and retain review evidence before HMRC or Companies House 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.