HMRC Company Tax Return filing is generally due 12 months after the accounting period end, while Corporation Tax payment is usually due earlier. Companies House accounts have separate statutory accounts deadlines, so UK iXBRL planning should track HMRC and Companies House dates separately.
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.
Do not use one deadline calendar
A UK iXBRL deadline plan should separate HMRC Company Tax Return filing, Corporation Tax payment and Companies House accounts filing. These dates can sit close together in workflow planning, but they are not the same legal deadline.
- Track HMRC Company Tax Return due date.
- Track Corporation Tax payment date separately.
- Track Companies House accounts deadline separately.
HMRC timing
GOV.UK states the Company Tax Return deadline is 12 months after the end of the accounting period it covers, with a separate Corporation Tax payment deadline that is usually 9 months and one day after the accounting period end.
- Build the iXBRL review timetable backwards from the HMRC return deadline.
- Leave time for CT600 and computation review.
- Retain evidence if late filing or appeal issues arise.
Companies House timing
Companies House accounts deadlines should be checked independently. Accounts filing evidence should be retained even where the same accounts source is used in the HMRC filing workflow.
- Confirm the applicable Companies House filing date.
- Account for approval/signature time before submission.
- Keep Companies House confirmation with the accounts record.
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 return deadline diarised.
- Corporation Tax payment date diarised.
- Companies House accounts deadline diarised.
- Internal review dates set before each deadline.
- Late filing exposure escalated early.
Official sources
Use these official references as the current regulatory baseline before making filing decisions.
FAQs
What is the short answer?
UK iXBRL Filing Deadlines 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.