CATO has closed — what limited companies need to do about CT600 filing in 2026
Direct Answer
HMRC's Company Accounts and Tax Online (CATO) service closed permanently on 31 March 2026. From 1 April 2026, every limited company must use commercial software to file its CT600 Corporation Tax return and annual accounts. There is no free HMRC alternative. Miss your deadline and you face an immediate £200 penalty. The easiest fix: appoint an accountant who already has compliant software and handles it for you.
What was CATO and what has replaced it?
CATO (Company Accounts and Tax Online) was HMRC's free online service that let limited companies file CT600 Corporation Tax returns and annual accounts directly — without paying for third-party software. It was widely used by small one-man companies and their accountants.
HMRC closed CATO on 31 March 2026 with no like-for-like free replacement. From 1 April 2026, all limited companies must use commercial software recognised by HMRC to submit CT600 returns and iXBRL-tagged accounts. There is no free HMRC filing portal for Corporation Tax.
If you or your accountant were still using CATO, you need a different solution now. This is not optional — HMRC will reject filings made through unsupported routes.
New penalty regime: what happens if you miss a filing deadline
The closure of CATO coincides with a tightened penalty regime for Corporation Tax. The key changes:
- Immediate £200 penalty for missing a Corporation Tax filing deadline — no grace period
- Further penalties for continued non-filing, escalating over time
- Interest charged on late payment of Corporation Tax, separate from filing penalties
CATO closing does not shift your filing deadline. If your company's accounting period ended 31 December 2025, your CT600 is still due by 31 December 2026. You now just need commercial software — or an accountant — to file it.
If you have been putting off finding a solution since CATO closed, the clock is already running. Check whether you need an accountant to handle this for you.
MTD for Corporation Tax: cancelled
There was a period when HMRC planned to extend Making Tax Digital to Corporation Tax — which would have meant quarterly digital reporting, not just an annual CT600. That plan has been cancelled.
HMRC confirmed there is no future timetable for MTD for Corporation Tax. The CT600 continues to be filed once per year, covering the company's accounting period. Commercial software is still required, but there is no quarterly reporting obligation for Corporation Tax.
This matters because it keeps the compliance burden manageable for one-man limited companies. Annual accounts, annual CT600, quarterly VAT (if VAT-registered) — that is still the full picture.
MTD for VAT: still mandatory
MTD for VAT has been mandatory since April 2022 and nothing has changed. If your limited company is VAT-registered, you must:
- Keep digital VAT records
- Submit VAT returns through MTD-compatible software
CATO never handled VAT returns — that was always a separate obligation. If you are on the standard VAT scheme, you submit quarterly. If you use the VAT flat rate scheme, the same digital submission rules apply.
Autobooks handles VAT returns as standard for all clients on the Gold plan (£89+VAT/month) and above.
MTD for Income Tax: does it affect contractor directors?
MTD for Income Tax came into force on 6 April 2026. It applies to sole traders and landlords with qualifying income over £50,000 in a tax year. This is not about your limited company — it is a personal tax obligation.
Most contractor directors are not affected, because their income comes through the company (salary and dividends — already reported via PAYE and SA100). But if you also have:
- Side self-employment income (freelance work outside the company) above £50,000, or
- Property rental income above £50,000
…then MTD for Income Tax applies to you personally. You will need to make quarterly digital updates to HMRC in addition to your normal Self Assessment return. If in doubt, talk to your accountant before the 2026-27 tax year ends.
What your options are now CATO is gone
You have three realistic choices:
- Buy commercial CT600 software yourself. Several providers exist at varying price points. You still need to understand how to prepare iXBRL-tagged accounts and file correctly — HMRC provides no guidance on using individual products.
- Use a DIY-focused service. Some online platforms offer self-service filing at a fixed fee. You prepare the numbers; they handle the submission. The risk: errors in the accounts or CT600 are your problem.
- Use an accountant. An accountant already has compliant software. Filings are handled as part of the service. Penalties for errors or late filing become their responsibility to manage, not yours.
For one-man limited companies, the maths often favours an accountant over buying and learning software yourself. Autobooks Gold costs £89+VAT/month and includes CT600, annual accounts, Companies House filing, VAT returns, payroll, bookkeeping, and SA100 — all in one. Compare that to software licence fees, your time, and the penalty risk of getting it wrong.
With CATO gone and penalties rising, now is the time to hand your company filings to the experts.
AutoBooks handles your Corporation Tax, VAT, and all HMRC obligations from £89+VAT/month — so you can focus on contracting.