HMRC's free Company Tax Return service has closed: how to file your CT600 now

If your company used to file its accounts and Company Tax Return through HMRC's free online service, that route has gone. HMRC closed the service on 31 March 2026. From 1 April 2026, Company Tax Returns go in through commercial software, either your own or your accountant's.

For many small companies this is the first year-end without it. If your accounting year ended on 31 March 2026, your return is due by 31 March 2027, so this is the year you need a new way to file. This guide covers what closed, your options now, how filing works step by step, what happened to the returns you filed before, and what's still the same at Companies House until April 2028.

What closed, and when

The service was called File your accounts and Company Tax Return. It let a small company that filed without an agent send its accounts to Companies House and its Company Tax Return to HMRC in one go, for free.

• 6 March 2025: HMRC announced the closure. HMRC said the service didn't meet modern digital standards or recent changes to company law.
• 31 March 2026: the service closed.
• 1 April 2026: companies file their return using commercial software.

What hasn't changed is the duty itself. The deadlines, the penalties and the contents of the return are the same as before. And if HMRC has sent you a notice to deliver a Company Tax Return, you must file it even if the company made a loss or has no Corporation Tax to pay.

Your options now

Choosing software from HMRC's list

HMRC says it accepts returns filed using any of the products on its list. The list groups suppliers by what they do:

• Produce and submit the CT600. Software that prepares and files the return itself.
• iXBRL integrated software. Products that produce tagged accounts and computations as part of the return.
• Managed tagging services. Someone tags your documents for you.
• Conversion software. Tools that turn your own documents into tagged files.

The list doesn't say what each product costs or whether any are free, so check the price before you commit. Also check that the product handles your kind of company and any supplementary pages you need. Some products file the accounts with Companies House in the same go. If yours doesn't, you file the accounts with Companies House separately (see below).

What goes in a Company Tax Return

A Company Tax Return is made up of:

• the CT600 form, plus any supplementary pages that apply to you
• your company accounts
• a tax computation, which shows how the profit in your accounts becomes your taxable profit

HMRC needs the accounts and the computation in iXBRL (Inline XBRL). An iXBRL file is a readable document with hidden tags behind each figure, so HMRC's systems can read the numbers. You don't tag anything by hand. The software does it, but HMRC says the company is responsible for the tags being right as well as the figures.

The computation is where taxable profit differs from accounting profit. Some costs in your accounts aren't allowed for tax, such as client entertaining, and depreciation is swapped for capital allowances. Our guide to Corporation Tax explains the rates and how marginal relief works.

How to file your return now, step by step

1. Find your dates. Your Company Tax Return is due 12 months after the end of the accounting period it covers. The tax itself is usually due 9 months and 1 day after the period ends, so you pay before you file.
2. Close the books for the year. Reconcile every bank account, and get invoices, bills and the director's loan account up to date.
3. Prepare the accounts and have the directors approve them.
4. Work out the taxable profit and the tax. This is the computation. The Corporation Tax calculator gives you an estimate to check against.
5. Pay the Corporation Tax by the payment deadline, which usually comes before the return is due.
6. File the return through your software or your accountant. You'll need the company's Unique Taxpayer Reference (UTR), which is on letters from HMRC. Keep the confirmation that it was received.
7. File the accounts with Companies House, unless your software has already sent them. A private company's accounts are usually due 9 months after its year-end.

An illustration: a company with a year-end of 31 March 2026 has its accounts due at Companies House by 31 December 2026. Its Corporation Tax is due by 1 January 2027, and its Company Tax Return by 31 March 2027.

What about the returns you filed before?

Returns filed through the old service can no longer be viewed or amended there. HMRC advised companies to download copies before it closed. If you did, keep them with your records.

If you didn't, here's where to look:

• Your accounts are on the public Companies House register. You can view and download past filings through the register's Find and update company information service.
• Your tax figures, such as losses carried forward, are on the old CT600 and computation. Check your own records and emails. If they've gone, ask your accountant, or contact HMRC.

You'll need last year's numbers. This year's accounts show them as comparatives, and losses carried forward reduce this year's taxable profit.

To change a return you've already filed, GOV.UK says to use commercial software, write to or send a paper return to HMRC's Corporation Tax office, or use an agent. You must usually make changes within 12 months of the filing deadline. To correct accounts already filed at Companies House, use software or send paper accounts by post.

What hasn't changed at Companies House (yet)

The old service filed your accounts with Companies House as well as your return with HMRC. That half still has its own routes.

• Accounts still go to Companies House every year, on the same deadline as before.
• Companies House's own online accounts service is still open, and you can still send paper accounts by post. Limited liability partnerships can only file certain package accounts online.

That changes on 1 April 2028. Companies House announced on 9 June 2026 that its accounts reforms will start then, rather than in April 2027 as first planned. From that date:

• every company files accounts using commercial software, in iXBRL, whether it files directly or through an agent
• the web and paper routes close for accounts. WebFiling stays open for other filings, such as the confirmation statement and director changes
• small and micro-entity companies must file a profit and loss account, though they can choose not to have it published on the register
• abridged accounts are no longer an option
• companies claiming audit exemption give a stronger statement that they qualify

If you've read that this starts in April 2027, that date is out of date. Companies House has moved it to April 2028.

Directors also have a separate Companies House job this year: identity verification. Existing directors give their personal code in the company's next confirmation statement.

Penalties for a late return

HMRC charges these penalties for a late Company Tax Return:

If a return is late three times in a row, each £200 penalty becomes £1,000.

If a return is more than 6 months late, HMRC can estimate the tax and write to you. This is called a tax determination, and you can't appeal it. You pay the tax and file the return, and HMRC then recalculates the interest and penalties.

If you had a reasonable excuse for filing late, you can appeal the penalty, but you have to file the return first. Interest is charged separately on Corporation Tax paid late. Late accounts at Companies House carry their own penalties too. Our guide to Companies House late filing penalties explains them.

What to have ready before you file

Whoever files, the return is only as good as the books behind it. Before you start, have:

• the year's books closed, with every bank account reconciled
• the director's loan account worked out. If you owe the company money at the year-end, the s455 calculator shows whether extra tax is due
• a list of assets bought in the year, for capital allowances
• last year's accounts and tax return, for comparatives and losses carried forward
• the company's UTR, plus the Companies House authentication code if you'll file the accounts yourself

Our limited company year-end checklist lists every task and deadline in date order.

Ledgers doesn't file the return for you. From the Starter plan (£29 a month ex VAT, see pricing), it produces a year-end pack and a draft Corporation Tax computation from your books, and tracks your Corporation Tax and annual accounts dates. Whoever files, you or your accountant, starts from finished numbers. You can invite your accountant on every plan, including Free. Start your books in Ledgers for free.

The short version

HMRC's free service closed on 31 March 2026. Your Company Tax Return now goes in through commercial software, yours or your accountant's, with the accounts and computation in iXBRL. Paper is only for a reasonable excuse or a return in Welsh. The deadlines haven't moved: pay 9 months and 1 day after your year-end, and file 12 months after it. At Companies House, nothing changes for accounts until 1 April 2028, when software filing becomes the only route.

Guidance only, not tax advice. Sources: GOV.UK, including Closure of the service to file your company accounts and tax return, Company Tax Returns, Company Tax Return obligations, penalties for late filing and Companies House's announcement on accounts filing from April 2028, as at 15 October 2026.