HMRC Free CT600 Deadline March 2026: Action Plan

HMRC's Free CT600 Service Has Closed — What to Do Now

If you've just discovered that HMRC's free online Corporation Tax filing service permanently closed on 31 March 2026, you're not alone. Thousands of UK company directors are now wondering what comes next.

The good news? Switching to commercial software is simpler than you might expect. This guide walks you through exactly what happened, what it means for your company, and what to do now.

What Happened?

HMRC permanently closed its free Corporation Tax online filing service on 31 March 2026.

Since that date, you can no longer:

• File your CT600 directly through HMRC's website
• Use the free HMRC software to prepare your return
• Submit Corporation Tax returns without third-party software

This affects every UK limited company required to file a return — whether you're actively trading, dormant, or winding down.

Why Did HMRC Do This?

HMRC has been gradually shifting tax return preparation and submission to commercial software providers. The free service was always limited — it lacked automatic calculations, error-checking, and the ability to handle anything beyond the most basic returns. Modern third-party software fills all of these gaps and delivers a better experience.

(Note: HMRC cancelled the planned Making Tax Digital for Corporation Tax programme in July 2025 — this closure is separate from that and is not connected to MTD.)

Who Needs to Take Action?

Every limited company registered for Corporation Tax in the UK that is required to file. Specifically:

• Active trading companies — you need software to file your next CT600
• Companies with upcoming deadlines — all CT600 filing deadlines after 31 March 2026 require commercial software
• First-time filers — new companies incorporated now have no access to the free service at all

What About Dormant Companies?

Once you have properly notified HMRC that your company is dormant, HMRC will normally stop issuing notices to deliver a CT600 — and no return is due unless HMRC specifically issues one. You are not required to file a CT600 every year simply to confirm dormancy.

If your dormant company does receive a notice to file from HMRC, you will need commercial software to submit the nil return — but that is a quick, straightforward process. If you haven't yet notified HMRC of dormancy, do so now.

Check Your Deadline

Your CT600 is due 12 months after the end of your accounting period. Any company with a filing deadline after 31 March 2026 must now use commercial software:

Your Action Plan: What to Do Right Now

Step 1: Check Your Filing Deadline

Log in to your HMRC Business Tax Account and check when your next CT600 is due. If your deadline has already passed, act immediately to file late — penalties increase with time.

Step 2: Gather Your Documents

Whether you're filing on time or catching up, you'll need:

• Company accounts (profit and loss, balance sheet)
• Bank statements for the accounting period
• Records of all income and expenses
• Details of any capital allowances (equipment purchases, vehicles)
• Director's loan account balance (if applicable)
• Your company's UTR number and Companies House number

Step 3: Choose Your Filing Software

Here's what to look for:

• HMRC-recognised — the software must be on HMRC's approved list
• iXBRL accounts generation — you need to submit tagged accounts alongside your CT600
• Auto-calculations — good software calculates your tax, including marginal relief
• Error checking — catches mistakes before submission
• Affordable — you shouldn't need to pay hundreds of pounds

Taxpipe is purpose-built for this exact situation. It's designed for directors who previously used HMRC's free service and need an affordable, straightforward alternative. You answer simple questions about your company, and Taxpipe handles the CT600, iXBRL accounts, and HMRC submission — all for a fraction of what an accountant charges. Check our pricing to see how it compares.

Step 4: Set Up Your Government Gateway

Whichever software you choose, you'll still need your HMRC Government Gateway credentials to authorise the submission. If you've been using the free service, you already have these. Keep them safe — you'll need them when your new software submits to HMRC.

Step 5: File a Test Return (If Time Allows)

If your next deadline isn't imminent, consider doing a trial run with your chosen software before the pressure is on. Most platforms (including Taxpipe) let you prepare your return and review it before submitting.

Common Questions

"Can I still file for free?"

Not through HMRC — the service closed on 31 March 2026. Some software providers offer competitively priced tiers for simple returns. Taxpipe offers straightforward pricing that's far less than hiring an accountant — use our calculator to estimate your costs.

"What if I miss the deadline because of the switchover?"

HMRC has not granted any grace period for the service closure. If you file late, the standard penalties apply. Note that HMRC increased the fixed penalties for CT600s with filing dates on or after 1 April 2026:

For CT600 filing dates BEFORE 1 April 2026:

• 1 day late: £100 penalty
• 3 months late: another £100
• 6 months late: 10% of unpaid tax (based on HMRC's estimate of the outstanding liability)
• 12 months late: a further 10% of unpaid tax

For CT600 filing dates ON OR AFTER 1 April 2026 (doubled penalties):

• 1 day late: £200 penalty
• 3 months late: another £200
• 6 months late: 10% of unpaid tax (based on HMRC's estimate of the outstanding liability)
• 12 months late: a further 10% of unpaid tax

The 6-month and 12-month charges apply only where there is unpaid tax — there is no fixed minimum amount for these tax-geared charges (unlike Self Assessment, Corporation Tax has no daily penalties or fixed minimum on the tax-geared element). Don't assume HMRC will be lenient because their service closed. Switch to new software now.

"I have a dormant company — do I really need to bother?"

Once you have properly notified HMRC that your company is dormant for Corporation Tax purposes, no CT600 is required unless HMRC sends you a specific notice to deliver a return. You do not need to file annually just to confirm dormancy — once notified, you're off the hook unless HMRC gets in touch.

If HMRC does issue a notice to file, a nil return via commercial software is quick and simple.

Not sure if you've properly notified HMRC? Log in to your Business Tax Account or call the HMRC Corporation Tax helpline on 0300 200 3410 to confirm.

"What about my accountant?"

If you already use an accountant, they'll handle the transition for you — they already use commercial software. This change primarily affects directors who file their own returns.

"Is my data safe with third-party software?"

Reputable providers use bank-level encryption and are authorised by HMRC. At Taxpipe, your data is encrypted at rest and in transit, and we never share it with third parties.

Don't Let Your Deadline Sneak Up on You

Even though the March 2026 closure has passed, your company's own filing deadline may still be months away. Here's why it pays to switch now rather than waiting:

1. Penalties accumulate — if your deadline has already passed, every day you delay adds risk
2. Learning curve — new software takes a little time to get comfortable with, even if it's simple
3. Missing documents — you might discover you're missing a bank statement or receipt
4. Support availability — software providers get swamped near popular deadlines

Our recommendation: switch to your new filing solution today.

The Silver Lining

Here's the thing most articles won't tell you: the HMRC free service was actually quite poor. It had no auto-calculations, no error checking, and no support. Many directors made mistakes without realising — overpaying tax or triggering HMRC enquiries.

Modern filing software like Taxpipe actually saves you money by:

• Automatically calculating marginal relief (which many directors miss, costing them thousands)
• Catching common errors before submission
• Generating iXBRL-tagged accounts automatically for micro-entity (FRS 105) companies
• Keeping records organised for future years

The switch from HMRC's free service isn't just necessary — it might be the best thing that's happened to your company's tax filing.

Next Steps

1. Check your deadline — know when your next CT600 is due
2. Sign up for Taxpipe — it takes 5 minutes to create an account
3. Use our corporation tax calculator to estimate what you'll owe
4. File with confidence — Taxpipe handles the technical complexity so you don't have to

HMRC's free service served its purpose, but its time has come. The sooner you make the switch, the less stressful filing season will be.

Need help choosing the right CT600 filing solution? Compare our pricing or try our corporation tax calculator to see what you'll owe this year.