File company accounts and the Company Tax Return as one controlled workflow.
Understand the separate Companies House, Corporation Tax payment and Company Tax Return deadlines, then prepare, review and retain the right filing evidence.
Three obligations, not one deadline
A private limited company commonly has three separate milestones: annual accounts to Companies House, payment of Corporation Tax to HMRC, and the Company Tax Return to HMRC. For a typical established private company, annual accounts are due nine months after the financial year end, Corporation Tax is usually payable nine months and one day after the Corporation Tax accounting period, and the return is usually due twelve months after that period ends.
First accounts and unusual accounting periods can create different dates. Treat the statutory deadline shown for the company and the HMRC accounting period as the controlling data rather than relying on a generic calendar reminder.
Build a filing control record first
Before preparing figures, record the identifiers and dates that control the job.
- Company name, number and Companies House authentication code
- Accounts start date, end date and Companies House filing deadline
- HMRC Unique Taxpayer Reference and Corporation Tax accounting period
- Corporation Tax payment deadline and Company Tax Return filing deadline
- Applicable accounts regime, audit status and accounting framework
Prepare one reconciled source of figures
Close the bookkeeping period, reconcile the bank, debtors, creditors, payroll, fixed assets, loans, taxes and equity, then document adjustments. The statutory accounts and tax computation serve different purposes, but both should reconcile to a controlled final trial balance.
Keep review notes with the filing record. A clear chain from source records to final accounts, tax adjustments and submitted artefacts makes later questions, corrections and repeat-year work easier to manage.
Review the filing package before submission
A pre-submission review should be more than checking whether the software has enabled a button.
- Confirm the legal entity, reporting period and return period
- Review the balance sheet, profit and loss account, notes and required statements
- Reconcile accounting profit to the Corporation Tax computation
- Check the CT600 and any required supplementary pages
- Validate iXBRL accounts and computations and inspect the human-readable output
- Record who prepared, reviewed and authorised the filing
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 company accounts and the Company Tax Return due on the same date?
Usually not. Companies House accounts, Corporation Tax payment and the Company Tax Return normally have separate deadlines.
What normally accompanies a Company Tax Return?
The online filing normally includes the CT600 plus iXBRL-tagged accounts and tax computations, with supplementary pages or other attachments where the company circumstances require them.
Can I assume acceptance if the software says submitted?
No. Retain and review the response from each filing authority. Submitted, rejected and accepted are different states.
Does this guide replace accounting or tax advice?
No. It is workflow guidance. The accounting treatment, disclosures, tax adjustments and relief claims require case-specific judgement.
Official sources
Checked on 2026-08-11. Official guidance takes priority if rules change.