CATO has closed — what are your options now?
By DormantFile · Updated 28 March 2026
HMRC shut down its free Corporation Tax Online service (CATO) on 31 March 2026. If you relied on CATO to file nil CT600 returns for a dormant company, you now need an alternative.
What was CATO?
CATO (Corporation Tax Online) was HMRC's free web-based tool for preparing and submitting CT600 Corporation Tax returns directly to HMRC. It was basic and not always intuitive, but it cost nothing. For directors of dormant companies filing nil returns, CATO was the obvious choice.
HMRC closed it on 31 March 2026 as part of a broader move to shift Corporation Tax filing to commercial third-party software.
What are the alternatives?
1. DormantFile — built for dormant companies
We built DormantFile in direct response to CATO closing. It handles both of the filings a dormant company needs:
- Nil CT600 submitted to HMRC via their GovTalk API
- Dormant accounts submitted to Companies House via their software filing API
Pricing starts at Basic £19/year for one company, £39/year for up to 10 companies on the Multiple plan, or £49/year for up to 100 companies on the Agent plan. See our pricing page for full details. No accounting knowledge needed, no features you don't need.
DormantFile handles dormant company filings only. If your company has traded or has transactions to report, you need accounting software or a professional.
2. Commercial accounting software
Packages like Xero, FreeAgent, Sage, and TaxCalc can file CT600 returns. These are full-featured accounting tools designed for trading companies — they handle invoicing, payroll, bank feeds, VAT, and more.
For a dormant company with zero transactions, this is significant overkill. Pricing typically starts at £100+/year and the software assumes you have actual accounting to do.
That said, if you already use one of these tools for a trading company, it may make sense to file your dormant company through the same software.
3. Hire an accountant
An accountant can file your CT600 on your behalf. For a nil return, expect to pay £80--£150 per company per year. This is the right choice if you are unsure whether your company qualifies as dormant, or if you want professional reassurance. For a straightforward nil filing, it is an expensive option.
4. Browse HMRC's approved software list
HMRC maintains a list of approved software providers that can submit CT600 returns on GOV.UK. Most options on this list are general-purpose accounting tools — very few are built specifically for dormant companies.
What about annual accounts?
CATO only handled CT600 returns, not annual accounts with Companies House. We cover how to handle those in our guide on how to file dormant company accounts. Companies House has its own free WebFiling service for accounts, or you can use DormantFile to handle both filings from one place. See how it works.
What if you don't file?
If your company is registered for Corporation Tax, you are legally required to file a CT600 return. Not filing results in:
- A £100 penalty if one day late
- Another £100 if three months late
- HMRC estimates your tax liability and charges 10% of the unpaid tax at six months
- A further 10% at twelve months
Companies House has its own separate late filing penalties for accounts.
Key points
- CATO closed on 31 March 2026. There is no longer a free way to file CT600 returns directly with HMRC.
- DormantFile is purpose-built for dormant companies, from £19/year, covering both CT600 and Companies House accounts.
- General accounting software works but is overkill for nil returns.
- An accountant is the right choice if you need professional advice.
- You still need to file annual accounts separately with Companies House — CATO never covered those.