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CT600 only, for companies that have filed their accounts Filed your accounts? Your tax return is still to do.

Filing annual accounts at Companies House does not file your Company Tax Return. The CT600 goes to HMRC, separately. We prepare and file it for you.

£39 per year-end
CT600 and tax computation, filed with HMRC
Files with HMRC only. Nothing is sent until you sign off.
Two separate filings, example company
Annual accounts
Companies House
Filed
Company Tax Return (CT600)
HMRC, with the tax computation
Not filed
Northgate Studio Ltd · year ended 31 Mar 2026 · fictional example

The mistake many company directors make

Accounts at Companies House. Tax return at HMRC. Two different filings.

Many directors file their annual accounts, often themselves, and assume they are done. The accounts are only half of the year-end.

Companies House

Annual accounts

Filed with Companies House. Due 9 months after your year end. This is the filing most people do.

HMRC

Company Tax Return (CT600)

Filed with HMRC, separately, along with the tax computation and a copy of the accounts. Due 12 months after the end of the accounting period.

The tax itself is a third date: Corporation Tax is usually due 9 months and 1 day after the end of the accounting period, even though the return is not due until 12 months after.

HMRC's free online service for filing accounts and the Company Tax Return closed on 31 March 2026. There is no free HMRC route now: from 1 April 2026 you need commercial software to file the CT600.

Late Company Tax Return penalties

£200 the day after the deadline.

These are the amounts GOV.UK publishes for returns with a filing date on or after 1 April 2026.

HMRC penalties for a late Company Tax Return
Time after the deadlinePenalty
The day after£200
3 monthsAnother £200 (£400 in total)
6 monthsHMRC estimates your Corporation Tax bill and adds a penalty of 10% of the unpaid tax
12 monthsAnother 10% of any unpaid tax
Late 3 times in a row£1,000, or £2,000 once 3 months late
Source: GOV.UK, Company Tax Returns: penalties for late filing Source: GOV.UK, increases to Corporation Tax late filing penalties

Penalty amounts can change. Check the GOV.UK pages for the current rules.

How CT600-only filing works

Your filed accounts are the starting point.

The AI rebuilds your year from your bank statements, then lines it up with the accounts you have already filed.

  1. Find your company

    Search by name or number. The app sees from Companies House that your accounts are filed and suggests the £39 CT600-only option.

  2. Upload your bank statements

    Drop in the CSV export from your business bank for the year. Any UK bank that exports a CSV works.

  3. The AI rebuilds the year

    It reads every transaction and matches the result to the accounts you already filed. The filed figures are the starting point.

  4. You confirm any differences

    If the bank data and the filed accounts do not agree, the differences are shown and you confirm them.

  5. It prepares the CT600 and computation

    Your filed accounts are attached from Companies House where possible. The return is checked against HMRC's validation rules before anything is sent.

  6. You sign off and it files with HMRC

    You review and sign off as director. It files with HMRC only. Nothing is sent to Companies House.

There is also an optional notes box, for anything you want the AI to know about the year.

What it does automatically

  • Pulls your company details, accounting period and deadlines from Companies House.
  • Reads last year's filed accounts from Companies House for your opening balances.
  • Reads the CSV export from any UK bank and maps the columns itself.
  • Categorises every transaction, and asks only about the ones your bank data can't explain.
  • Reads documents from your previous accountant (PDF, images or Excel), such as last year's accounts, tax computation or trial balance.
  • Fills in the filing form from Companies House data.
  • Checks everything against HMRC's validation rules before anything is sent.

CT600-only pricing

£39 for the tax return.

Per year-end. For companies that have already filed their accounts at Companies House.

CT600 only
£39per year-end

We prepare and file your Company Tax Return with HMRC. You review and sign off as director.

File my CT600 only
  • CT600 and tax computation
  • Starts from the accounts you already filed
  • Differences shown for you to confirm
  • Checked against HMRC's validation rules
  • Filed with HMRC only
Haven't filed your accounts yet?
£49per year-end

Annual accounts and Company Tax Return, prepared and filed with Companies House and HMRC.

See what is included

With a qualified accountant's review: £125 per year-end.

Frequently asked questions

Ask away.

Does filing my accounts at Companies House file my Company Tax Return?
No. They are two separate filings. Annual accounts go to Companies House. The Company Tax Return (CT600) goes to HMRC, with the tax computation and a copy of the accounts.
Is there a free HMRC way to file the CT600?
No longer. HMRC's free online service for filing accounts and the Company Tax Return closed on 31 March 2026. From 1 April 2026 you need commercial software to file with HMRC.
When is my CT600 due?
The Company Tax Return is due 12 months after the end of the accounting period it covers. The Corporation Tax itself is usually due 9 months and 1 day after the period ends.
What are the penalties for a late Company Tax Return?
For returns with a filing date on or after 1 April 2026, HMRC charges £200 the day after the deadline and another £200 at 3 months, £400 in total. At 6 months HMRC estimates your Corporation Tax bill and adds a penalty of 10% of the unpaid tax, and another 10% at 12 months. If the return is late 3 times in a row, the £200 penalties rise to £1,000, or £2,000 once it is 3 months late.
How does the CT600-only service work?
You find your company and upload your bank statements as a CSV. The AI rebuilds the year and matches it to the accounts you already filed, starting from the filed figures. Any differences are shown and you confirm them. It then prepares the CT600 and tax computation, attaches your filed accounts from Companies House where possible, and files with HMRC only, after you sign off.
How does it know my accounts are already filed?
When you pick your company, the app checks the Companies House filing history. If the accounts for the period are filed, it suggests the £39 CT600-only option. You can change the choice.
What if my bank statements and my filed accounts do not agree?
The differences are shown to you and you confirm them. The filed accounts are the starting point.
What do I need?
Your company name or number and a CSV export of your business bank statements for the period. There is also an optional notes box for anything the AI should know about the year.
Does it file my accounts again?
No. A CT600-only filing goes to HMRC only. Nothing is sent to Companies House.
What if I have not filed my accounts yet?
Choose the £49 option instead. It prepares and files the annual accounts and the CT600 together.

Get your CT600 filed for £39.

Upload your bank statements when you are ready. Nothing is sent until you sign.

File my CT600 only — £39