HMRC Penalties for Late Corporation Tax Filing
You missed the deadline. Maybe the year-end crept up on you, maybe the accountant dropped the ball, or maybe you simply didn't know when your CT600 was due. Whatever the reason, HMRC's penalty regime for late corporation tax filing is automatic, escalating, and surprisingly expensive.
This guide breaks down every penalty tier, interest rate, and surcharge you could face — plus exactly what to do if you've already missed the deadline.
When Is Your CT600 Due?
Your company tax return (CT600) must be filed with HMRC within 12 months of the end of the accounting period it covers.
Your corporation tax payment is due earlier — 9 months and 1 day after the accounting period end.
| Accounting period end | CT600 filing deadline | Tax payment deadline |
|---|---|---|
| 31 March 2026 | 31 March 2027 | 1 January 2027 |
| 31 December 2025 | 31 December 2026 | 1 October 2026 |
| 30 June 2026 | 30 June 2027 | 1 April 2027 |
Critical distinction: Filing the return late and paying the tax late trigger different penalties. You can face both simultaneously.
Late Filing Penalties: The Escalating Scale
HMRC imposes automatic penalties that increase the longer you delay. No warnings, no grace periods — the clock starts the day after your deadline.
The penalty timetable
| Delay | Penalty | Cumulative total |
|---|---|---|
| 1 day late | £100 flat penalty | £100 |
| 3 months late | Another £100 flat penalty | £200 |
| 6 months late | HMRC estimates your tax bill and charges 10% of the unpaid tax (minimum £300) | £200 + 10% of tax |
| 12 months late | Another 10% of the unpaid tax (minimum £300) | £200 + 20% of tax |
How the 6-month and 12-month penalties work
At 6 months, HMRC issues a tax determination — their own estimate of what you owe. This estimate is often high because HMRC bases it on whatever information they have (which may not account for your expenses and reliefs). The 10% penalty is calculated on this estimated amount.
At 12 months, a second 10% penalty is added. So if HMRC estimates your tax bill at £10,000:
- 6-month penalty: £1,000 (10% of £10,000)
- 12-month penalty: £1,000 (10% of £10,000)
- Plus the two flat £100 penalties
- Total penalties: £2,200 — before you've even paid the tax itself
Repeat offenders
If your CT600 was also late for the previous accounting period, the two flat £100 penalties increase to £500 each. So habitual late filers face:
- 1 day late: £500
- 3 months late: £500
- Total flat penalties: £1,000 (instead of £200)
This makes serial late filing very costly — and HMRC tracks filing history, so there's no avoiding the uplift.
Late Payment Penalties and Interest
Separate from filing penalties, paying your corporation tax late triggers interest charges — and potentially additional penalties.
Late payment interest
Interest runs automatically from the day after the payment deadline (9 months and 1 day after your year-end) until the date HMRC receives payment. The current rate:
- Late payment interest rate: 7.25% per annum (as of February 2026)
This rate has been historically high following Bank of England base rate increases. For context, it was just 2.6% in early 2022.
Example
Your company owes £15,000 in corporation tax. The payment deadline was 1 January 2026, but you don't pay until 1 July 2026 — 6 months late.
Interest: £15,000 × 7.25% × (181/365) = £539.38
That's on top of any filing penalties.
Late payment surcharges
For corporation tax, HMRC doesn't currently impose separate late payment penalties in the same way as for income tax. However, the late payment interest is compulsory and non-negotiable. Interest accrues daily, even if you're in a payment arrangement with HMRC.
What Happens If You Never File?
If you simply don't file your CT600 at all:
- Penalties accumulate up to the 12-month cap (£200 + 20% of estimated tax)
- HMRC issues a tax determination — their estimate of what you owe. This becomes legally binding unless you file the actual return
- The estimated tax is collected through the normal enforcement process (debt collection, county court judgments, potential winding-up petitions)
- Your company may be struck off — HMRC can object to voluntary strike-off if returns are outstanding, or Companies House may strike off the company if confirmation statements are also overdue
- Director liability — In extreme cases, HMRC can pursue directors personally, especially if there's evidence of deliberate non-compliance
Warning: A tax determination cannot be appealed. The only way to replace it is to file the actual CT600 return. Even if it's years late, filing the return replaces HMRC's estimate with your actual figures — which are usually lower.
How to Check If You Have Outstanding Penalties
You can check your penalty position through:
- HMRC online services — Log in to your company's HMRC account and check the "View account" section
- CT603 notice — HMRC sends a "Notice to deliver a return" which states the filing deadline. If you've missed it, penalties will follow
- Penalty notices — HMRC sends separate penalty assessment letters (SA371 or similar) for each penalty tier
- Phone HMRC — Call the Corporation Tax helpline on 0300 200 3410
Can You Appeal a Late Filing Penalty?
Yes, but only on specific grounds. HMRC accepts appeals based on reasonable excuse — circumstances beyond your control that prevented timely filing.
What qualifies as a reasonable excuse
| Accepted | Not accepted |
|---|---|
| Serious illness or hospitalisation of the person responsible | "I didn't know the deadline" |
| Death of a close relative close to the deadline | "My accountant was busy" |
| HMRC online service outage on the deadline day | "I couldn't afford an accountant" |
| Fire, flood, or theft destroying records | "I was waiting for bank statements" |
| Postal delays (if filing by post, which is rare) | "I didn't think my dormant company needed to file" |
| Partner or service provider failure (in some circumstances) | "I forgot" |
How to appeal
- Within 30 days of the penalty notice — appeal online through your HMRC account or write to the address on the penalty notice
- After 30 days — you can still appeal but must explain why the appeal is late
- Provide evidence — medical certificates, insurance claims, HMRC service outage records
- Escalate if rejected — if HMRC refuses your appeal, you can request an independent review or appeal to the First-tier Tribunal
The "I filed late but owe no tax" argument
If your company had no taxable profits (e.g., it was dormant or made losses), the 6-month and 12-month percentage penalties will be nil (10% of zero = zero). But the flat penalties (£100 or £500 each) still apply. You cannot escape flat penalties just because no tax is due.
How to Avoid Late Filing Penalties
Prevention is far cheaper than penalties. Here's a practical checklist:
1. Know your deadline
Your filing deadline is 12 months after your accounting period end. If your year-end is 31 March, you must file by 31 March of the following year. Don't confuse this with the payment deadline, which is 3 months earlier.
2. File early
There's no advantage to waiting until the last minute. Filing early doesn't mean paying early — the tax payment date stays the same regardless of when you file. Filing your CT600 within a few months of your year-end gives you a comfortable buffer.
3. Set calendar reminders
Set reminders at:
- 3 months after year-end — start preparing accounts
- 6 months after year-end — accounts should be nearly ready
- 9 months after year-end — tax payment due (file the return too)
- 11 months after year-end — final warning before the filing deadline
4. Use filing software
Modern CT600 filing tools like Taxpipe let you prepare and submit your return without waiting for an accountant. If your company is straightforward — trading income, standard expenses, no complex reliefs — you can file your CT600 yourself in an afternoon.
5. File nil returns for dormant companies
Even if your company did nothing all year, you must file a CT600. A nil return takes minutes to prepare and avoids penalties entirely.
What If You've Already Missed the Deadline?
If you're reading this and your deadline has already passed:
-
File immediately. Every day you delay risks moving into the next penalty tier. If you're at 2 months, file before the 3-month mark to avoid the second £100 penalty.
-
Pay any tax owed. Interest is running daily. Even a partial payment reduces the interest accumulating.
-
Consider an appeal. If you have a genuine reasonable excuse, appeal within 30 days of receiving the penalty notice.
-
Contact HMRC about payment plans. If you can't pay the full amount, HMRC's Business Payment Support Service (0300 200 3835) can arrange a Time to Pay agreement. This doesn't remove penalties, but it stops enforcement action.
-
Don't ignore it. The penalties and interest keep growing. HMRC won't forget, and the longer you leave it, the worse it gets.
File Your CT600 with Taxpipe
Don't risk penalties by leaving your CT600 to the last minute. Taxpipe makes it straightforward to file your company tax return online — no accountant required, no complex software.
- Guided process — answer questions about your company and Taxpipe builds the return
- iXBRL included — accounts are generated and tagged automatically
- HMRC submission — file directly to HMRC through Taxpipe
- Fraction of the cost of an accountant
Frequently Asked Questions
What is the penalty for filing a CT600 one day late?
£100, applied automatically with no warning or grace period. If your previous CT600 was also late, this increases to £500. The penalty applies even if no corporation tax is owed.
How much interest does HMRC charge on late corporation tax?
The current late payment interest rate is 7.25% per annum (as of February 2026). Interest runs daily from the day after the payment deadline until the date HMRC receives full payment.
Can I avoid the 6-month penalty by filing before 6 months?
Yes. If you file your CT600 before the 6-month mark, you only face the flat penalties (£100 at 1 day and £100 at 3 months). The 10% tax-based penalties only kick in at 6 and 12 months.
Do dormant companies get late filing penalties?
Yes. Even if your company is dormant and owes no tax, you must still file a CT600. The flat £100/£500 penalties apply to all late returns regardless of the tax position. The percentage-based penalties (10% of tax) would be nil since no tax is due.
Can my accountant be held responsible for late filing penalties?
No. HMRC holds the company (and ultimately its directors) responsible for filing on time. If your accountant filed late, your legal recourse is against the accountant through their professional body or a civil claim — but HMRC will still collect the penalty from your company.
What happens if HMRC issues a tax determination?
A tax determination is HMRC's own estimate of your tax liability, issued when you haven't filed after 6 months. It becomes a legally enforceable debt. You cannot appeal a determination — the only way to replace it is to file the actual CT600 return, even if it's years late. File as soon as possible because the determination is usually higher than your actual liability.