What Happens If I File Company Tax Late? (UK Penalties Explained)
Short version. What happens if you file your company tax late in the UK? Current HMRC flat penalties, interest and Companies House late filing fees explained.
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Missing your corporation tax filing deadline can be expensive. HMRC and Companies House both impose penalties, and they're separate, so you could face charges from both bodies.
Here's exactly what happens, what it costs, and what you can do about it.
The Two Deadlines You Need to Know
Your UK limited company has two key filing deadlines after each accounting period ends:
| Filing | Deadline | Filed With |
|---|---|---|
| Annual accounts | 9 months after period end | Companies House |
| CT600 corporation tax return | 12 months after period end | HMRC |
| Corporation tax payment | 9 months + 1 day after period end | HMRC |
Example: If your accounting period ends 31 March 2026:
- Accounts due at Companies House: 31 December 2026
- Corporation tax payment due: 1 January 2027
- CT600 return due at HMRC: 31 March 2027
HMRC Penalties for Late CT600 Filing
HMRC imposes flat-rate penalties for late CT600 returns. The rates below apply where the filing date is on or after 1 April 2026.
| How Late | Penalty |
|---|---|
| Filed within 3 months after the deadline | £200 |
| Filed more than 3 months after the deadline | £400 |
| Third and later consecutive late return, within 3 months | £1,000 |
| Third and later consecutive late return, more than 3 months | £2,000 |
Important Notes:
- The flat-rate penalty can apply even if the company owes no tax, for example where it made a loss
- If 3 or more consecutive returns are late, the increased £1,000 or £2,000 rate can apply
- These penalties are on top of any interest charged on late tax payments
- For older filing dates, lower flat-rate penalties may apply. Check the penalty notice and HMRC guidance for the period concerned
HMRC Interest on Late Payment
If you pay your corporation tax late (after the 9 months + 1 day deadline), HMRC charges interest from the day after the deadline until the date you pay. The current late payment interest rate is regularly updated — check HMRC's website for the latest rate.
Interest is charged automatically. Even a few weeks' delay can add up.
Companies House Penalties for Late Accounts
Companies House penalties for late accounts are separate from HMRC penalties and are not negotiable:
| How Late | Private Company Penalty |
|---|---|
| Up to 1 month | £150 |
| 1 to 3 months | £375 |
| 3 to 6 months | £750 |
| Over 6 months | £1,500 |
Key Points:
- These penalties double if you were late the previous year
- Penalties are imposed on the company, not the director personally (but directors are responsible for ensuring compliance)
- Unlike HMRC, Companies House does not reduce penalties for companies that owe no tax — the penalty is for late filing regardless
Total Cost of Being Late: An Example
Scenario: Your accounts period ended 31 March 2026. Your return and accounts are both filed 4 months late, and the CT600 filing deadline falls on or after 1 April 2026.
| Penalty | Amount |
|---|---|
| HMRC: return filed more than 3 months late | £400 |
| Companies House: accounts filed 3-6 months late | £750 |
| HMRC: Interest on late tax payment (~4 months) | Variable |
| Flat penalties before interest | £1,150 |
For a company that might only owe a few hundred pounds in tax, these penalties can exceed the actual tax liability.
What If You've Already Missed the Deadline?
File as Soon as Possible
The penalties increase over time, so every day counts. File immediately to prevent further penalties from accumulating.
You Can Appeal HMRC Penalties
You may be able to appeal if you have a "reasonable excuse" such as:
- Serious illness or bereavement
- HMRC's online service was unavailable
- Fire, flood, or theft affecting your records
- A partner or close relative died shortly before the deadline
HMRC does not consider the following as reasonable excuses:
- You didn't know about the deadline
- You relied on someone else to file
- You didn't receive a reminder
- You didn't owe any tax
Companies House Appeals
Companies House rarely accepts appeals. Their position is that directors should know their filing deadlines. However, you can apply for an extension before the deadline if you know you'll be late.
How to Avoid Late Filing
- Know your deadlines — mark them in your calendar as soon as your accounting period ends
- Don't wait until the last minute — start preparing your accounts at least 2-3 months before the deadline
- Use software — tools like SimpleCompanyTax can prepare your CT600 and accounts same-day
- Set reminders — at 6 months, 3 months, and 1 month before each deadline
- File even if you can't pay — filing your return on time avoids the filing penalties, even if you need more time to pay the tax
Dormant Companies Are Not Exempt
Dormancy does not remove every filing obligation. Check each authority separately:
- Dormant accounts at Companies House
- Any CT600 requested by an outstanding HMRC notice, unless HMRC withdraws it. Once HMRC knows the company is dormant, recurring returns are not normally required unless requested.
A never-traded company should tell HMRC it is dormant. A company that stops trading must also deal with its outstanding active-period return. Neither situation cancels a notice automatically. See HMRC's guidance.
Summary
Late filing is expensive and entirely avoidable. The key deadlines are 9 months for Companies House accounts, 9 months and 1 day for tax payment, and 12 months for the CT600 after the accounting period ends. HMRC flat penalties for a filing date on or after 1 April 2026 start at £200, while Companies House penalties have separate rates.
The cheapest approach: file on time. The fastest approach: use software that can prepare everything in a single session.