CT600 Filing Changes Timeline: 2025-2027 Complete Guide
Major changes are coming to how UK companies file their Corporation Tax returns and statutory accounts. This timeline covers everything you need to know from now until April 2027.
Quick Reference: Key Dates
| Date | Change |
|---|---|
| 31 March 2026 | HMRC's free CT600 service (CATO) closes |
| 1 April 2026 | CT600 filing requires commercial software |
| 1 April 2027 | Companies House WebFiling for accounts closes |
| 1 April 2027 | Paper filing for accounts ends |
| 1 April 2027 | Abridged accounts abolished |
Detailed Timeline
Now - December 2025
Status: Both HMRC and Companies House free services fully operational
What to do:
- Download your HMRC filing history (CT600 returns, computations, accounts)
- Research and choose commercial software
- Create an account with your chosen software
- Understand the upcoming changes
- Avoid last-minute rush
- Learn new software without deadline pressure
- Secure your filing history before access is removed
January - March 2026
Status: Final months of HMRC's free service
What happens:
- HMRC's Company Accounts and Tax Online (CATO) remains available
- Growing awareness leads to increased demand on the service
- Software providers may see high signup volumes
- Complete any outstanding CT600 filings through HMRC
- Final download of any missing filing history
- Ensure new software is tested and working
- File at least one return through new software as practice
31 March 2026: HMRC Service Closes
The change:
- HMRC's Company Accounts and Tax Online (CATO) shuts down permanently
- No more free online CT600 filing through HMRC
- Access to previously filed returns through CATO is removed
- You cannot file CT600 returns through HMRC's website
- You cannot view or download past submissions from CATO
- The joint filing service (CT600 + accounts to Companies House) ends
- Charities registered with HMRC may apply for paper filing
- Community amateur sports clubs (CASCs) may apply for exemption
- Some dormant companies may qualify
1 April 2026: Software-Only CT600 Filing
From this date:
- All CT600 returns must be filed using commercial software
- Software can be free (like TinyTax) or paid
- Filing obligations remain unchanged
- Same 12-month deadline from accounting period end
- CT600 form itself
- Filing deadlines
- Payment methods (bank transfer, Direct Debit, etc.)
- iXBRL requirements for accounts
April 2026 - March 2027
Status: CT600 software-only; Companies House WebFiling still available
What to do:
- File all CT600 returns through commercial software
- Begin preparing for Companies House changes
- Understand new disclosure requirements (for micro-entities)
- Assess impact of losing abridged accounts option
1 April 2027: Companies House WebFiling Closes
The changes:
- Companies House WebFiling for accounts ends
- Paper filing for accounts ends
- Abridged accounts option abolished
- All accounts must be filed using commercial software
- Must file balance sheet AND profit and loss account
- Previously only balance sheet was required for micro-entities
- More financial information becomes public
- Must file balance sheet, P&L, directors' report
- Auditor's report (unless audit exempt)
- No more filleted (abbreviated) option
- Companies House WebFiling for confirmation statements
- WebFiling for director changes
- WebFiling for other statutory filings
April 2027 Onwards
New normal:
- All CT600 returns filed via commercial software
- All statutory accounts filed via commercial software
- iXBRL mandatory for all filings
- Enhanced disclosure requirements
- Greater transparency on public register
Why Are These Changes Happening?
The Legislation
The Economic Crime and Corporate Transparency Act (ECCTA) 2023 requires:
- Enhanced verification of company information
- Improved data quality through software validation
- Mandatory digital filing with structured data
- Greater corporate transparency
The Technical Reasons
HMRC and Companies House systems:
- Built on legacy technology
- Cannot support modern validation requirements
- Cannot handle new iXBRL tagging requirements
- Costly to maintain and update
The Policy Goals
Government objectives:
- Reduce company register fraud
- Improve accuracy of financial information
- Enable automated analysis and monitoring
- Align with international standards
Impact by Company Type
Trading Micro-Entities
| Aspect | Before | After April 2027 |
|---|---|---|
| CT600 filing | HMRC free or software | Software only |
| Accounts filing | WebFiling or software | Software only |
| P&L disclosure | Optional | Mandatory |
| Filing method | Free available | Free software available |
Dormant Companies
| Aspect | Before | After |
|---|---|---|
| CT600 | Not required (if no liability) | Same |
| Accounts | WebFiling (simple) | Software (simple accounts) |
| Effort | Minimal | Slightly more (software needed) |
Small Companies
| Aspect | Before | After April 2027 |
|---|---|---|
| CT600 filing | HMRC free or software | Software only |
| Accounts filing | WebFiling or software | Software only |
| Abridged option | Available | Abolished |
| Disclosure | Can abbreviate | Full accounts required |
Action Checklist
Before March 2026
- Download all HMRC filing history
- Choose and set up CT600 software
- Test software with a real filing
- Train staff on new processes
Before April 2027
- Understand new disclosure requirements
- Ensure software handles Companies House filing
- Update internal processes for accounts preparation
- Plan for increased public disclosure
Frequently Asked Questions
Will deadlines change?
No. CT600 filing deadline remains 12 months from accounting period end. Accounts filing deadline remains 9 months (private companies).Do I have to pay now?
No. Free options like TinyTax exist for micro-entity companies.What if I have multiple companies?
Each company needs to file through software. Some software supports multiple companies.Can my accountant still file for me?
Yes. Accountants use software to file on clients' behalf. This doesn't change.Are these dates confirmed?
Yes. The dates are set by the Economic Crime and Corporate Transparency Act 2023.Summary
- March 2026: HMRC free CT600 service closes
- April 2026: CT600 requires commercial software
- April 2027: Companies House WebFiling closes for accounts
- April 2027: Abridged accounts abolished
- Free options exist — you don't have to pay
TinyTax offers free CT600 and accounts filing. Get started today →