How to Calculate Late Filing Penalties for Your Company Tax Return
Every UK limited company must file a company tax return with HMRC each year. Miss the deadline and HMRC will issue fixed penalties — regardless of whether you owe any tax or your company made any profit at all. This guide explains exactly how the penalties work, what they cost, and how to work out what you might owe.
Key Dates: Filing vs Payment
Before calculating any potential penalty, it helps to understand two entirely separate deadlines:
Filing deadline: Your company tax return must be submitted within 12 months of the end of your accounting period. For a company whose accounting period ended on 31 March 2025, the filing deadline is 31 March 2026.
Payment deadline: Corporation tax is due 9 months and 1 day after your accounting period ends — this comes before the filing deadline. For a 31 March 2025 period end, payment is due by 1 January 2026.
These are separate obligations with different consequences. This guide covers late filing penalties only. If you also paid your tax late, HMRC charges interest separately — see our guide to HMRC late payment interest on corporation tax.
Current Penalty Rates
HMRC uses a tiered structure: the longer you delay, the higher the penalties. There are two types of charge:
- Fixed penalties — applied regardless of your tax position
- Tax-geared penalties — a percentage of unpaid corporation tax, applied at 6 and 12 months late
Fixed Penalties for Returns with a Filing Date Before 1 April 2026
| How late | Penalty |
|---|---|
| 1 day late | £100 |
| More than 3 months late | Additional £100 (total £200) |
| How late | Penalty |
|---|---|
| Within 3 months | £500 |
| More than 3 months | £1,000 |
New Penalty Rates From 1 April 2026
Following Autumn Budget 2024, HMRC is doubling fixed late filing penalties. The new rates apply to any return with a filing date on or after 1 April 2026 — even if the accounting period ended earlier.
| Offence | Current penalty | From 1 April 2026 |
|---|---|---|
| Within 3 months late | £100 | £200 |
| More than 3 months late | £200 | £400 |
| Repeat offender — within 3 months | £500 | £1,000 |
| Repeat offender — more than 3 months | £1,000 | £2,000 |
Tax-Geared Penalties
In addition to fixed penalties, HMRC applies percentage charges based on unpaid corporation tax:
- 6 months late: 10% of any unpaid corporation tax on top of fixed penalties
- 12 months late: A further 10% of unpaid corporation tax
- 18 months after the period end: Up to 20% of unpaid tax if the return remains unfiled
How to Calculate Your Penalty
Follow these steps to work out your potential exposure:
Step 1 — Identify your filing deadline. Add exactly 12 months to the last day of your accounting period.
Step 2 — Count how many months late you are. Measure from the day after your filing deadline to the date you actually filed (or today, if the return is still outstanding).
Step 3 — Apply the fixed penalty table. £100 from day one; an additional £100 once you pass 3 months. Apply the doubled figures if your return's filing date falls on or after 1 April 2026.
Step 4 — Check for tax-geared penalties. Are you 6 or more months late? If corporation tax remains unpaid, add 10% of that amount. At 12 months late, add another 10%. At 18 months from the period end, HMRC can impose a further charge of up to 20%.
Step 5 — Check for repeat offender status. Has your company filed late for each of the previous two consecutive years? If so, the fixed penalties increase significantly.
Worked Examples
Example 1: First-Time Late Filing, 5 Weeks Late
Scenario: Accounting period ended 30 June 2024. Filing deadline: 30 June 2025. Return filed on 4 August 2025 — 35 days late.
Calculation:
- Fixed penalty: £100 (1 day to 3 months)
- Tax-geared penalty: none (within 3 months)
Example 2: First-Time Late Filing, 5 Months Late, Tax Paid on Time
Scenario: Same company, but the return is filed in November 2025 — 5 months after the deadline. Corporation tax of £8,000 was paid on time in January 2025.
Calculation:
- £100 (1 day late)
- £100 (3+ months late)
- Tax-geared penalty: none (tax was paid on time)
Example 3: First-Time Late Filing, 7 Months Late, Tax Unpaid
Scenario: Return filed 7 months after the deadline. Corporation tax of £20,000 still outstanding.
Calculation:
- £100 (fixed)
- £100 (3+ months late)
- £2,000 (10% of £20,000 unpaid tax — 6+ months late)
Example 4: Repeat Late Filer, 4 Months Late, From April 2026
Scenario: Company has filed late for the previous two consecutive years. The return has a filing date of 1 June 2026 (4 months after the deadline). No unpaid tax.
Calculation (new rates apply):
- £1,000 (repeat offender, more than 3 months — new rate)
Note: Under the current (pre-2026) rules, this same scenario would cost only £1,000. Under the new rules it is also £1,000 — but for a first-time late filer in the same scenario, the cost doubles from £200 to £400.
Zero Tax Owed? Penalties Still Apply
A common misconception is that penalties do not apply if your company made no profit. Fixed penalties — £100 and £200, or from April 2026, £200 and £400 — apply regardless of your tax position. Dormant companies, zero-profit years, and loss-making periods all carry the same filing obligation.
Having no tax liability does help with the percentage-based penalties: 10% of nil tax owed is nil. But the fixed penalties are unavoidable once the deadline passes.
Tax Determinations
If your return remains outstanding 6 months after the filing deadline, HMRC can issue a tax determination — their estimate of how much you owe. You cannot appeal a determination, and HMRC will pursue collection based on their estimate. Filing your actual return is the only way to replace a determination with your correct figures.
This is one of the stronger reasons to file promptly even if you cannot pay immediately. The determination amount may well exceed your actual liability.
Appealing a Penalty
HMRC may cancel a penalty if you have a reasonable excuse — for example, a serious or unexpected illness, a bereavement close to the deadline, or a documented failure of HMRC's own online systems. Relying on an accountant who then failed to file is generally not accepted as a reasonable excuse, though you may have a separate civil claim against them.
How to appeal:
- File your overdue return first — HMRC will not consider an appeal until the return is submitted
- Submit your appeal within 30 days of the penalty notice date
- Include your UTR, the penalty notice date, the penalty amount, and the accounting period end date
Understanding Your Tax Liability
Tax-geared penalties are calculated on unpaid corporation tax. Your company's total profits determine how much tax is owed in the first place. See our guide to CT600 Box 410: Total Profits for a detailed explanation of how HMRC calculates your taxable profits for the period.
Summary
Late filing penalties for UK company tax returns start at £100 from the first day and escalate significantly for persistent non-compliance or large unpaid tax bills. Crucially, fixed penalties apply even when no tax is owed. From 1 April 2026, fixed penalties double under new HMRC rules — making timely filing more important than ever. If you have already missed your deadline, file as soon as possible to cap your exposure, avoid a tax determination, and preserve your right to appeal.