HMRC CT600 Alternative: Best Free Options for 2026

With HMRC's free CT600 filing service closing on 31 March 2026, over 1.5 million UK companies need to find alternative software. The good news? Free alternatives exist that are actually better than HMRC's ageing system.

Why You Need an Alternative

HMRC's Company Accounts and Tax Online (CATO) service has been available since 2011, but it's shutting down due to:

  • Outdated technology that can't support modern filing requirements
  • Changes required by the Economic Crime and Corporate Transparency Act 2023
  • The shift to mandatory iXBRL filing with enhanced validation
After 31 March 2026, you cannot file a CT600 through HMRC's website. You must use commercial software.

What to Look for in CT600 Software

When choosing an HMRC alternative, consider:

Essential Features

  • HMRC-recognised — Must be approved to submit CT600 returns electronically
  • iXBRL generation — Required for accounts attached to your CT600
  • Companies House filing — Ideally handles both HMRC and Companies House submissions
  • Error checking — Catches mistakes before submission

Nice to Have

  • Trial balance import — Saves hours if you use Xero, QuickBooks, or Sage
  • Tax calculation — Automatic corporation tax computation
  • Guidance — Built-in help for each CT600 box
  • Historical records — Store past submissions for reference

Free CT600 Alternatives

TinyTax (Recommended)

Cost: Free for micro-entity companies

TinyTax is purpose-built as a free replacement for HMRC's service. It offers:

  • Complete CT600 filing — Prepare and submit directly to HMRC
  • iXBRL accounts — Automatic generation for Companies House
  • Dual submission — File to both HMRC and Companies House
  • Trial balance import — From Xero, QuickBooks, and other accounting software
  • Error prevention — Validates your return before submission
  • No subscription — Genuinely free, not a trial
Best for: Small companies wanting to continue filing themselves without paying fees.

Try TinyTax free →

Government Gateway (Partial)

Cost: Free

You can still access Government Gateway after CATO closes, but only for:

  • Viewing submitted returns
  • Paying Corporation Tax
  • Managing your company's tax affairs
You cannot file CT600 returns through Government Gateway after March 2026.

If you need more advanced features, paid options include:

TaxCalc

Cost: From £100+ per year

  • Comprehensive tax return software
  • Multiple company support
  • Used by many accountants
Best for: Accountants managing multiple clients

IRIS

Cost: £200+ per year

  • Professional-grade software
  • Integrates with IRIS accounts
  • Training and support included
Best for: Larger practices and established accountants

Sage

Cost: £150+ per year

  • Integration with Sage accounting
  • Corporation tax and accounts
  • Additional modules available
Best for: Companies already using Sage software

BTCSoftware

Cost: £100+ per year

  • Standalone CT600 filing
  • iXBRL accounts
  • Used by accountants
Best for: Accountants wanting dedicated filing software

Feature Comparison

FeatureTinyTaxTaxCalcIRISSage
CT600 filing✓✓✓✓
iXBRL accounts✓✓✓✓
Companies House filing✓✓✓✓
Trial balance import✓✓✓✓
Free for micro-entities✓✗✗✗
No subscription required✓✗✗✗
Error checking✓✓✓✓

How to Switch from HMRC

Switching to alternative software is straightforward:

  1. Download your HMRC history — Save your past returns before CATO closes
  2. Create an account — Register with your chosen software
  3. Enter company details — Company number, UTR, accounting period
  4. Import or enter figures — From your accounts or trial balance
  5. Review and submit — The software handles HMRC submission
You don't need to notify HMRC that you're switching software.

When to Switch

Now. Don't wait until March 2026. Benefits of switching early:

  • Learn the software without deadline pressure
  • Resolve any issues before HMRC's service closes
  • Take advantage of better error checking immediately
  • Ensure your next filing goes smoothly

Frequently Asked Questions

Is there really free CT600 software?

Yes. TinyTax offers completely free CT600 filing for micro-entity companies. There are no hidden fees, trials, or subscription requirements.

What if I'm not a micro-entity?

TinyTax works for small companies too. Larger companies may need more advanced software like TaxCalc or IRIS.

Can I still use an accountant?

Absolutely. Many accountants use software like TinyTax, TaxCalc, or IRIS to file on behalf of their clients. Ask your accountant what they recommend.

What happens to my HMRC account?

Your Government Gateway account remains active for other HMRC services. You just won't be able to file CT600 returns through it after March 2026.

Do I need different software for Companies House?

Not necessarily. TinyTax and other comprehensive solutions handle both HMRC CT600 filing and Companies House accounts filing in one place.

Summary

  • HMRC's free CT600 service closes 31 March 2026
  • Free alternatives like TinyTax exist and offer better features
  • Paid options suit accountants and larger companies
  • Switch early to avoid last-minute problems
  • You don't need to notify HMRC when you change software

Ready to switch? TinyTax offers free CT600 filing with no subscription. Create your account today →