If your company filed its CT600 a day late last year, that cost you £100. From 1 April 2026, the same mistake costs £200. HMRC has doubled every fixed penalty for late corporation tax returns - the first increase since 1998 - and repeat offenders now face fines up to £2,000 before tax-geared charges even start.
TL;DR: HMRC doubled fixed corporation tax late filing penalties from 1 April 2026. A late return now costs £200 (was £100), rising to £400 after three months (was £200). File late three times in a row and you're looking at £1,000 or £2,000 per return. These apply whether you owe tax or not. The change affects any return with a filing date on or after 1 April 2026.
What Changed on 1 April 2026?
Fixed penalties under Schedule 18 of the Finance Act 1998 doubled across the board. HMRC had not increased these amounts since they were introduced 28 years ago, and in real terms the old fines were worth about half their original value (GOV.UK, 2026). The government expects the increase to bring in £45 million to £70 million per year.
Here is how the old and new rates compare:
| Situation | Old penalty | New penalty |
|---|---|---|
| Return filed late | £100 | £200 |
| Still outstanding after 3 months | £200 | £400 |
| 3 successive late filings (under 3 months) | £500 | £1,000 |
| 3 successive late filings (over 3 months) | £1,000 | £2,000 |
These are flat-rate charges. They apply whether your company owes corporation tax or not - dormant companies and zero-liability businesses are caught too.
Who Does This Affect?
Every incorporated business in the UK with a filing date on or after 1 April 2026. That covers a large number of companies - there were 5.66 million active companies on the Companies House register as of early 2026 (NatWest/Beauhurst Startup Index, 2026). In our experience, many directors of smaller companies don't realise their CT600 is due even when no tax is owed.
The measure targets a real problem. HMRC's published tax gap data shows the overall gap reached £46.8 billion at a rate of 5.3% for 2023-24 (GOV.UK, 2025). Small businesses now account for 60% of that gap, up from 48% five years earlier (BDO, 2025).
How Do Tax-Geared Penalties Stack on Top?
The fixed fines are only the starting point. If your return is more than six months late, HMRC will estimate your tax bill and add a penalty of 10% of the unpaid corporation tax. Leave it twelve months and another 10% is added - meaning you could face charges equal to 20% of your liability on top of the fixed fines (GOV.UK, 2026).
What we see most often is directors who miss the filing deadline, assume the damage is done, and then leave it a few more months. That turns a £200 problem into a £400 fixed penalty plus a tax-geared charge that can run into thousands.
What About Late Payment Interest?
Late payment interest sits at 7.75% from January 2026, calculated daily (GOV.UK, 2026). That rate reflects the Bank of England base rate plus 4% - HMRC widened this margin from base rate plus 2.5% in April 2025.
On a £50,000 corporation tax bill paid three months late, the interest alone comes to around £970. Add the £400 fixed penalty for a return filed over three months late and you're already past £1,300 before any tax-geared surcharges.
Filing and payment deadlines are separate. Your CT600 is due 12 months after the end of your accounting period. Corporation tax payment is due earlier - nine months and one day after your accounting period ends. Missing both triggers penalties from two different regimes. We covered the payment penalty rules separately if you want the full picture.
Does This Apply to Dormant Companies?
Yes. A dormant company with no corporation tax liability still needs to file a CT600 unless HMRC has formally agreed it is dormant. One question clients always ask is whether they can avoid this by telling Companies House the company is dormant - but Companies House dormancy and HMRC dormancy are different statuses. You need to notify HMRC directly.
If your dormant company has a filing date on or after 1 April 2026 and you miss it, you'll face the same £200 penalty as a trading company.
What Should You Do Now?
Three steps to stay out of trouble:
First, check your filing deadline. Log in to your HMRC online account or ask your accountant to confirm the due date for your current accounting period. If your year end was 31 March 2026, your CT600 is due by 31 March 2027 - which falls under the new penalty regime.
Second, separate filing from payment in your calendar. The payment deadline (nine months and one day) comes first. The filing deadline (twelve months) comes later. Missing either carries its own penalties. Our year-end accounts checklist covers both deadlines along with the Companies House annual accounts filing.
Third, set up reminders at least 30 days before each deadline. If you use an accountant, confirm they have your correct year-end date on file and understand the new penalty structure. If you're looking for a firm to handle your corporation tax filing and compliance, that's what we do. With Making Tax Digital rolling out further changes, keeping your digital records up to date through the year makes filing faster when the deadline arrives.
Frequently Asked Questions
Do the new penalties apply to my current return?
Only if your filing date falls on or after 1 April 2026. If your accounting period ended on 31 March 2025, your CT600 was due by 31 March 2026 - the old penalties still apply. But if your year end was 1 April 2025 or later, you're on the new rates.
Can I appeal a late filing penalty?
Yes. You can appeal within 30 days of the penalty notice if you have a reasonable excuse - things like serious illness, a close family bereavement, or an HMRC systems failure. "I forgot" or "my accountant was busy" typically don't qualify.
Are these the same penalties as Companies House late filing?
No. HMRC penalties for late CT600 returns are separate from Companies House penalties for late annual accounts. You could face fines from both if your accounts and tax return are overdue. Companies House penalties for a private company range from £150 to £1,500 depending on how late you are.
What if my company made no profit?
You still need to file. The fixed penalties apply regardless of your tax liability. Even a company that made a loss and owes zero corporation tax will be fined £200 for a late return.
Not sure where your company stands on its CT600 deadline? Get in touch - we'll check your filing dates, flag any upcoming deadlines, and make sure your return is submitted on time under the new penalty rules.