HMRC and Companies House have confirmed that from 1 April, all businesses must use compliant, commercial software to file their company’s tax returns.

As of 31 March, the free joint online service, commonly known as the CATO portal, from these two Government bodies has been removed and you must now use software to file company tax returns to HMRC.

For the time being, you will still be able to file annual accounts at Companies House using third-party software, WebFiling services or paper filing.

The decision has been made to end this service as it is “outdated and no longer aligns with modern digital standards”, according to Companies House.

This change is in line with the introduction of the Economic Crime and Corporate Transparency Act, which implemented “enhanced corporation tax requirements and changes to UK company law.”

It also follows on from a major IT security breach at Companies House, identified in March 2026, that exposed the WebFiling system and allowed some users to potentially access and amend the details of other companies.

Although the breach has now been resolved and security strengthened, it has raised concerns about the reliability of GOV.UK One Login service.

Can you still amend previous returns using the free service?

HMRC and Companies House have confirmed that now that the free filing service has closed, company directors will have to use commercial tax software if they need to make changes to a previously submitted Corporation Tax return or refile a rejected return.

From now onwards, any previously filed financial information will no longer be available in the system, as it has not been retained and will need to be entered again.

HMRC has said that, for amendments, it will also be acceptable to send a paper return to the Corporation Tax Services office.

If you have previously filed financial accounts with Companies House and you want to make changes or corrections, this will also need to be done via commercial software or by sending paper accounts to Companies House via post.

Are there any exceptions to this new rule?

Companies can file a paper Corporation Tax return only in limited circumstances, such as if they wish to submit it in Welsh or can demonstrate a valid, reasonable excuse to HMRC. Otherwise, returns must be filed online using commercial software.

If you are affected by this change and need help choosing and utilising commercial software to complete your Corporation Tax return, please speak to our team.