Company filing is moving from mixed web and paper routes toward structured software workflows.
The 2026 HMRC service closure and 2028 Companies House accounts transition are separate changes with a common operational consequence: software readiness must be tested early.
31 March 2026: joint service closure
The former joint online service for company accounts and Company Tax Returns closed on 31 March 2026. From 1 April 2026, previous users need commercial software for HMRC Company Tax Return filing.
2026 onward: current CT600 and taxonomy maintenance
Corporation Tax software must keep pace with HMRC return artefacts, accepted taxonomies and service changes. A static claim that software is “CT600 ready” is less useful than a maintained version-and-validation process.
1 April 2028: software-only Companies House accounts
Companies House says accounts filed on or after 1 April 2028 must be submitted using commercial software in iXBRL. This is a distinct implementation date from the 2026 HMRC service closure.
Operational implications
The transition affects more than the submission screen.
- Structured source data and iXBRL production
- Authentication and presenter credentials
- Accounts-type and supplementary-page coverage
- Reviewer and authoriser workflows
- Submission evidence and rejection handling
- Supplier continuity and data export
What remains subject to implementation guidance
Companies House has also announced changes affecting small-company and micro-entity accounts. The detailed filing and publication mechanics should be taken from the final guidance in force for the filing date, not inferred from earlier policy summaries.
Where professional judgement is needed
This guide explains a filing workflow, not the accounting treatment, tax position or legal duties of a particular company. Confirm the applicable accounting framework, reliefs, disclosures and filing obligations against current official guidance and, where needed, a qualified accountant or tax adviser.
FAQ
Are the 2026 and 2028 changes the same?
No. The 2026 change closed the former joint service; the 2028 change makes Companies House accounts filing software-only.
Why does iXBRL matter?
It combines readable accounts with machine-readable tags used in structured electronic filing and validation.
What should software users monitor?
Monitor official implementation dates, CT600 artefacts, accepted taxonomies, accounts-type coverage and authority service guidance.
Official sources
Checked on 2026-08-11. Official guidance takes priority if rules change.