HMRC Joint Filing Service (CATO) Has Closed: What Companies Need to Know

If you’ve previously used HMRC and Companies House’s free Joint Filing Service (formerly known as CATO) to submit your annual accounts and Corporation Tax return together, it’s important to know that this option is no longer available. Since 1 April 2026, Corporation Tax returns must be filed using HMRC-recognised commercial software.

What should you do now?

The Joint Filing Service (often referred to as CATO) closed permanently on 31 March 2026. For many years, it allowed smaller companies to submit their annual accounts to Companies House and their Corporation Tax return (CT600) to HMRC through a single online process. That service has now been withdrawn.

In practical terms, from 1 April 2026:

Company Tax Returns (CT600) must be submitted using HMRC-recognised commercial software, except in very limited circumstances where paper filing is permitted.
Annual accounts and Corporation Tax returns are now separate submissions.
Historic returns can no longer be accessed through the former Joint Filing Service portal.

What has changed?

It’s worth noting that Companies House WebFiling remains available for annual accounts. Although Companies House intends to move towards software-only filing in the future, that change has been paused, and businesses will receive at least 21 months’ notice before any new requirement comes into force.

What does this mean for your business?

If J. Dauman & Co. already prepares your annual accounts and Corporation Tax return, there’s nothing you need to do. We already file through HMRC-recognised commercial software as standard, so this change won’t affect your existing service.

The biggest impact is on directors who have been filing their own Corporation Tax returns using the free Joint Filing Service. If you’ve relied on that option in previous years, you’ll now need suitable commercial software or professional support. It’s far better to put those arrangements in place now than wait until your filing deadline approaches.

It’s also worth checking that you have copies of previous submissions. While filed accounts remain available through Companies House, historic Corporation Tax returns are no longer accessible through the former Joint Filing Service portal.

Review how you’ll file your next Corporation Tax return well before your deadline — the change is already in force.
Keep copies of previous accounts and tax returns in a safe place.
Decide whether to use HMRC-recognised software or appoint an accountant to prepare and submit your return.
If you file your own return, make sure your software supports iXBRL where required.
Keep track of both your Companies House and Corporation Tax filing deadlines. Annual accounts and Corporation Tax returns are now separate submissions, so it’s important to stay on top of both.

For many businesses, this is a good opportunity to review whether managing these filings in-house remains the most efficient approach. At J. Dauman & Co., we prepare and submit annual accounts and Corporation Tax returns accurately and on time, while helping clients identify valuable tax-saving opportunities wherever possible.

Frequently asked questions

Can I still file my accounts with Companies House for free?

Yes. Companies House WebFiling remains available for eligible annual accounts while the move to mandatory software filing is on hold. Companies will receive at least 21 months’ notice before that changes.

Is the Joint Filing Service the same as Companies House WebFiling?

No. The Joint Filing Service allowed companies to submit both their Corporation Tax return and annual accounts together. Companies House WebFiling remains available for eligible accounts filings, while Corporation Tax returns must now be submitted separately using HMRC-recognised commercial software.

Do I need to buy software if my accountant files my return?

No. Your accountant will use their own recognised commercial software to prepare and submit your Corporation Tax return, so there’s no need for you to purchase anything.

Can I still access returns submitted through the old service?

Not through the former Joint Filing Service portal. Companies House accounts remain publicly available, and copies of Corporation Tax returns can be requested from HMRC. If you need help rebuilding your records, we can assist.

Does this affect dormant companies?

Dormant companies must still meet their Companies House filing obligations, which can currently be done through WebFiling where applicable. If HMRC requires a Corporation Tax return, it must now be submitted using recognised commercial software.

Need advice?

Not sure how you’ll file your next Corporation Tax return?

Whether you’ve previously relied on HMRC’s free Joint Filing Service or simply want peace of mind that everything is filed correctly, our team is here to help. We’ll ensure your annual accounts and Corporation Tax returns are prepared accurately, submitted on time and fully compliant, allowing you to focus on running your business with confidence.