Many companies file their accounts at Companies House first — through Tax Optimiser, another agent, or on paper — and only then turn to the Company Tax Return. You can file just the CT600 in Tax Optimiser, but there is one thing to understand first: HMRC needs a full set of accounts with the return, and Tax Optimiser builds that set from the figures in your accounting period. So the period has to hold the same accounts you filed at Companies House.
What HMRC needs, and why it differs from Companies House
Most small companies file filleted accounts at Companies House: the balance sheet and notes, without the profit and loss account or the directors’ report. HMRC instead expects the full statutory accounts — the same accounts the directors approved, including the profit and loss account and directors’ report — attached to the CT600 in iXBRL format, together with the tax computation.
Tax Optimiser produces both versions from the same trial balance, notes and directors, and always attaches the full version to the CT600. You can’t upload a copy of accounts prepared elsewhere, so the figures need to be entered in the period. See Full or filleted: what gets filed where for more on the two versions.
Heads up — the full accounts sent to HMRC must be the same accounts the directors approved. Every balance sheet figure should match the filing at Companies House, and the profit for the year should match the approved profit and loss account.
Set up the period to match the filed accounts
- Period dates. Use exactly the start and end dates of the accounts you filed. If HMRC’s notice to file covers different dates, keep the accounts dates on the period and use CT Dates → Override on the period Overview for the return.
- Accounts Type. Choose the same standard used for the filed accounts — FRS 105 (micro-entity) or FRS 102 Section 1A (small company). Set this before entering figures: changing it later clears the trial balance and notes.
- Prior year. If the filed accounts showed prior-year figures, enter those too so the comparatives match.
Enter the figures
Enter the trial balance the filed accounts were prepared from, using whichever route suits you: Simple Entry, a trial balance import, a Xero or QuickBooks connection, or manual entry. Then complete the parts of the accounts that aren’t figures:
- the directors (and who signed the accounts) and the registered office;
- the notes the filed accounts carried, such as the average number of employees, guarantees and any advances to directors;
- the principal activity, which appears in the directors’ report.
Use the same approval date
Open the Corporation Tax computation and, on the General tab, set the Directors’ signage date (box 980) to the date the directors approved the accounts — the date printed on the balance sheet you filed at Companies House. The CT600 can’t be sent without it.
Mark Companies House as not required
On the period Overview, next to Companies house Status, click Mark as not required. This hides the Companies House submission and its checklist for the period, so nobody files the accounts a second time. View Accounts stays available, because the accounts are still needed for the CT600. If you change your mind, click Mark as required.
Check the accounts match before you send
Download the accounts you filed from the Companies House register (the company’s Filing history) and compare them with the Review Document step of the Corporation Tax submission wizard, which shows exactly what HMRC will receive. Check:
- total assets, net current assets and net assets;
- share capital and reserves;
- the prior-year column, if there is one;
- the approval date and the director who signed;
- the accounts standard and the notes.
The profit and loss account and directors’ report appear only in the HMRC version if you filed filleted accounts — that is expected. Check the profit for the year against the directors’ approved accounts and against the movement in reserves on the balance sheet.
Tax Optimiser doesn’t compare the two filings for you, so this check matters. If something doesn’t match, correct the figures in the period rather than filing accounts that differ from the approved set.
Submit the CT600
Review the computation, then open Corp Tax Submission and work through the wizard as usual: confirm the client has approved the accounts, review the accounts and the computation, choose the director accepting the declaration, and send. See Submitting to HMRC and Companies House for each step.
Common questions
Can I upload the PDF of the accounts I filed instead?
Not for a company. HMRC requires companies to attach accounts in iXBRL, and Tax Optimiser generates that from the period. Uploading a PDF is only available for structures outside the Companies Act, such as clubs and charitable incorporated organisations.
My accounts were filed by another accountant. Do I need their trial balance?
It is the quickest route. Failing that, work back from the filed balance sheet and the approved profit and loss account: every line in the accounts needs a matching figure in the trial balance.
Will marking Companies House as not required affect the CT600?
No. It only hides the Companies House filing for that period. The CT600 and the accounts attached to it are unaffected.
Does the made-up-to date at Companies House matter?
No. Once accounts are filed, Companies House moves the company’s next made-up-to date on, so the Corporation Tax wizard doesn’t warn about it.