Free CT600 Filing: Complete Guide to Free Options

Filing a CT600 corporation tax return doesn't have to be expensive. Several options exist for UK companies wanting to file without paying hefty software fees.

This guide explains your free filing options, what's changing in 2026, and how to choose the right solution for your company.

The Free Filing Landscape is Changing

For years, HMRC offered a free online service for small companies to file their CT600 returns. This service will close permanently on 31 March 2026.

After this date, all companies must use commercial software to file corporation tax returns. HMRC has stated the current system "doesn't meet modern digital standards" and the commercial software market has matured since online filing launched in 2011.

Important: If you've been using HMRC's free service, download and save your last three years of filed returns before 31 March 2026. You won't be able to access them after the service closes.

Current Free CT600 Filing Options

1. HMRC's Free Online Service (Until March 2026)

HMRC's own filing service remains available until 31 March 2026. It's designed for small, unrepresented companies with straightforward tax affairs.

What's included:

  • CT600 form completion and submission
  • Supplementary pages CT600A, CT600E, and CT600J
  • Basic tax calculations
  • Direct submission to HMRC
What's NOT included:
  • iXBRL accounts generation
  • Companies House filing
  • Complex supplementary pages
  • Support for accounting periods over 12 months
Limitations: You'll still need separate software to create iXBRL accounts for Companies House. The service only handles the CT600 itself.

2. Free Trials and Pay-Per-File Options

Several commercial software providers offer free trials or let you prepare returns for free, only charging when you submit.

TinyTax lets you search for your company, enter your figures, and see your calculated tax liability before committing. You only pay when ready to file.

Easy Digital Filing offers a similar model — prepare for free, pay to submit.

This "try before you buy" approach means you can:

  • Check the software works for your situation
  • See your tax calculation before paying
  • Compare different options without commitment

3. Accountancy Software with CT600 Included

If you already pay for accounting software, check whether CT600 filing is included in your subscription.

FreeAgent includes CT600 filing for micro-entities in its subscription (from £14.50/month). If you're already a FreeAgent user, this represents "free" CT600 filing since you're paying for the accounting software anyway.

However, this isn't truly free — you're paying for the broader accounting package.

What "Free" Really Means

When evaluating free options, consider the full picture:

Hidden Costs to Watch For

  • Separate iXBRL accounts — Some free CT600 tools don't include accounts generation. You may need to pay separately for iXBRL accounts.
  • Companies House filing — Not all CT600 software handles Companies House. Filing accounts separately adds complexity.
  • Support limitations — Free services often have limited or no support.
  • Feature restrictions — Free tiers may not support your specific situation (property companies, extended periods, etc.).

True Cost of "Free" HMRC Filing

Using HMRC's free CT600 service still requires:

  1. Separate iXBRL accounts software (typically £30-100)
  2. Separate Companies House submission
  3. More time managing two separate filings
An all-in-one paid solution may actually save money when you factor in time and the cost of separate accounts software.

Who Qualifies for Micro-Entity Status?

Most free and low-cost filing options target micro-entities. You qualify as a micro-entity if you meet two of these three criteria:

  • Turnover: £1 million or less
  • Balance sheet total: £500,000 or less
  • Employees: 10 or fewer
These thresholds increased in April 2025. Most small limited companies qualify.

Micro-entities can file simplified accounts with just a balance sheet — no profit and loss account required publicly. This makes filing simpler and most software supports it.

Preparing for April 2026

With HMRC's free service closing, now is the time to:

1. Evaluate Commercial Software

Don't wait until the deadline. Test different options while HMRC's service is still available as a backup.

Look for software that handles:

  • CT600 submission to HMRC
  • iXBRL accounts generation
  • Companies House filing
  • Your specific company type (trading, dormant, property, etc.)

2. Download Your Filing History

Before March 2026, log into HMRC's service and download:

  • Your last three CT600 submissions
  • Any computations or supporting documents
  • Notes on how you calculated specific figures
You won't be able to access this history after the service closes.

3. Consider All-in-One Solutions

Software that handles both HMRC and Companies House filing from one form saves significant time. You enter your figures once and file to both organisations.

TinyTax offers this all-in-one approach for micro-entities — CT600, iXBRL accounts, and computations generated from a single set of data.

Free CT600 Filing Checklist

Before choosing a free option, verify it covers:

  • CT600 form generation and submission
  • Tax calculation (including marginal relief if applicable)
  • iXBRL computations
  • iXBRL accounts for Companies House
  • Your company type (trading/dormant/property)
  • Your accounting period length
  • Direct HMRC submission via Government Gateway
  • Companies House submission (if needed)
If any boxes are unchecked, you'll need additional software or manual work.

Filing Your CT600 with TinyTax

TinyTax provides an affordable all-in-one solution for UK micro-entities:

  1. Search for your company using your company number
  2. Enter your financial figures with guided forms
  3. Review calculated tax before committing
  4. Generate all documents — CT600, accounts, computations
  5. Submit to HMRC and Companies House in one session
The pay-per-filing model means you only pay when ready to submit. No subscription, no ongoing fees.

Frequently Asked Questions

Is HMRC CT600 filing really free?

Yes, until 31 March 2026. However, you still need separate software to create iXBRL accounts for Companies House, which typically costs £30-100.

What happens after HMRC's free service closes?

From 1 April 2026, all companies must use commercial software to file CT600 returns. You'll need HMRC-recognised software from their approved supplier list.

Can I file a CT600 completely free after 2026?

Unlikely. While some software offers free trials or preparation, you'll need to pay to actually submit your return. The days of completely free CT600 filing are ending.

What's the cheapest way to file a CT600?

Pay-per-file software is typically cheapest for single companies. Look for options that include iXBRL accounts to avoid paying separately. Compare the total cost including accounts, not just the CT600.

Do I need separate software for Companies House?

Not necessarily. Some CT600 software (like TinyTax) includes Companies House filing. Others require separate accounts software. Check before choosing.

Can I use free software if I have a property company?

Some free options don't support property companies well. Rental income has specific tax treatment — verify your chosen software handles it correctly.

Next Steps

Ready to file your CT600? Search for your company on TinyTax to see how the process works. You can enter your figures and see your tax calculation before deciding whether to proceed.