Key takeaways

  • HMRC's free 'File your accounts and Company Tax Return' service, known as CATO, closed on 31 March 2026.
  • Since 1 April 2026 you must use commercial software to file your Company Tax Return (CT600) and accounts with HMRC.
  • A paper Company Tax Return is accepted only if you have a reasonable excuse or are filing in Welsh.
  • You must still file accounts with Companies House separately; WebFiling still accepts dormant, micro-entity, abridged and small full accounts until 31 March 2028.
  • From 1 April 2028, all companies must file accounts with Companies House in iXBRL format using commercial software, and web and paper accounts filing closes.
  • HMRC's software supplier list, updated 12 October 2026, has a 'Suitable for self-filers' column, but HMRC does not recommend or endorse any product.
  • Deadlines are unchanged: accounts to Companies House within 9 months of the year end, the CT600 within 12 months and Corporation Tax usually 9 months and 1 day after.

HMRC’s free Company Accounts and Tax Online (CATO) service closed on 31 March 2026, so you now need commercial software to file your Company Tax Return and accounts with HMRC. Your accounts still go to Companies House separately, and you can still use its WebFiling service or paper for most small company accounts until 31 March 2028. The filing deadlines have not changed.

What was CATO and why did it close?

CATO was HMRC’s free joint service that let small companies file their accounts with Companies House and their Company Tax Return with HMRC in one go. HMRC announced the closure on 6 March 2025.

HMRC said the service was outdated and did not meet current digital standards, Corporation Tax requirements or company law changes under the Economic Crime and Corporate Transparency Act 2023. The closure also supports Companies House reforms such as identity verification.

How to file now: the two separate filings

You now make two filings, usually through different routes.

FilingWho toHow
Annual accountsCompanies HouseWebFiling, software or paper (until 31 March 2028)
CT600 and accounts and computations in iXBRLHMRCCommercial software only

GOV.UK’s closure guidance, last updated 1 April 2026, says you must continue to file annual accounts with Companies House. Filing with HMRC does not count as filing with Companies House.

Filing your Company Tax Return without CATO

You must use commercial software to file with HMRC from 1 April 2026. A paper return is accepted only if you have a reasonable excuse or are filing in Welsh.

  1. Pick software. Use HMRC’s list of commercial software suppliers, updated 12 October 2026. Check the “Produce and submit CT600” and “Suitable for self-filers” columns if you file yourself.
  2. Prepare the return. The software produces the CT600, tagged accounts and tax computations.
  3. Submit it to HMRC through the software.
  4. Pay the tax. Corporation Tax is usually due 9 months and 1 day after the end of the accounting period.

HMRC says it cannot recommend or endorse any one product, and does not support them. Some products on the list are marked as not suitable for self-filers. The list does not show prices, so compare them yourself. Our CT600 guide explains the return.

Filing your accounts with Companies House

You can still file with Companies House in three ways until 1 April 2028. Companies House says:

  • WebFiling accepts dormant accounts for companies that have never traded, micro-entity accounts, abridged accounts and small full accounts.
  • Commercial software files accounts in iXBRL and can handle some package accounts WebFiling cannot.
  • Paper accounts can be posted to Companies House in Cardiff (Crown Way, CF14 3UZ), though processing is slower.

Community interest company accounts cannot go through WebFiling. If you want to change or correct accounts already filed, you must use software or paper. See our guides to filing accounts at Companies House and micro-entity accounts.

Which route applies to you?

  • If your company is dormant and has never traded, file dormant accounts on WebFiling, and check whether HMRC needs a return.
  • If you file micro-entity or small accounts yourself, use WebFiling for Companies House and HMRC-listed software for the CT600.
  • If you want one product for both, choose software that files the CT600 with HMRC and accounts with Companies House.
  • If you use an accountant, nothing changes for you; they file through their own software.

Deadlines and penalties

The deadlines are the same as before CATO closed. Private companies must file accounts within 9 months of the accounting reference date; first accounts are due within 21 months of incorporation. The Company Tax Return is due 12 months after the end of the accounting period.

Late filingCompanies House (private company)HMRC (CT600)
Up to 1 month£150£200 from day 1
3 to 6 months£750Another £200 at 3 months
Over 6 months£1,50010% of unpaid tax at 6 months

Companies House charges £375 for accounts 1 to 3 months late. HMRC raises each £200 penalty to £1,000 if a return is late three times in a row. Use our filing deadline calculator to work out your dates.

What changes in April 2028

From 1 April 2028, every company must file accounts with Companies House in iXBRL using commercial software. Companies House confirmed on 23 October 2026 that web and paper filing will close for accounts then. WebFiling stays open for other filings, such as confirmation statements.

The planned requirement for small companies and micro-entities to file a profit and loss account is paused. See Companies House pauses P&L filing.

What to do now

  • Keep your own copies of past accounts and returns; filings made through CATO could not be accessed there after 1 April 2026.
  • Choose software for your next CT600 well before the deadline.
  • Diary your Companies House and HMRC deadlines separately.
  • Plan to move accounts filing to software before April 2028.

Frequently asked questions

Is there still a free way to file a Company Tax Return?

HMRC no longer offers a free filing service. You must use commercial software, and HMRC’s supplier list does not show prices, so check each product’s charges.

Can I still use Companies House WebFiling for my accounts?

Yes, until 31 March 2028, for dormant, micro-entity, abridged and small full accounts. From 1 April 2028 you must use software.

Can I file a paper CT600 now CATO has closed?

Only if you have a reasonable excuse or are filing in Welsh. Otherwise HMRC expects an online return through software.

Do I still need to file accounts with Companies House if I file with HMRC?

Yes. GOV.UK says you must continue to file annual accounts with Companies House separately.

Can I get my old CATO filings back?

Not through CATO, as previous filings could not be accessed there after 1 April 2026. Check your own saved copies or ask your accountant.

Sources

Rates, thresholds and rules in this guide were checked against HMRC and GOV.UK guidance on 6 November 2026. Tax rules change, so check the current position on GOV.UK or with a qualified adviser before acting. This guide is general information, not personal advice.