When do I need to file a CT600 return?

A CT600 Corporation Tax return must be filed within 12 months of the end of your company’s accounting period, even if no tax is due.

What happens if I file my Corporation Tax return late?

HMRC imposes automatic penalties for late CT600 filing: £100 for 1 day late, another £100 after 3 months, and additional 10% surcharges at 6 and 12 months. Repeated late filings can attract fines of up to £500 per incident.

Can I request an extension to file Corporation Tax?

You can request extra time by contacting HMRC. Extensions may be granted for reasonable excuses such as system failure, illness, or other events outside your control, but interest on unpaid tax may still apply.

How can I pay my Corporation Tax?

You can pay Corporation Tax via Faster Payments, CHAPS, BACS, Direct Debit, debit/credit card, or from overseas using HMRC international bank details. Always include your 17-character CT payment reference.

What are the key Corporation Tax deadlines I should remember?

Key deadlines include: paying Corporation Tax 9 months and 1 day after year end, filing CT600 within 12 months of year end, notifying HMRC when the company starts trading, and quarterly instalments for large companies.

Can I appeal late filing penalties?

Yes, you can appeal penalties if you have a reasonable excuse. Keep evidence such as emails, screenshots, or medical documents, and submit your appeal promptly to HMRC.

Do I have to pay Corporation Tax if my company made no profit?

If your company has no taxable profits, Corporation Tax may not be payable, but you still need to submit a CT600 return to HMRC.

What counts as the accounting period for Corporation Tax?

The accounting period for Corporation Tax is usually the same as your company’s financial year. It begins when your company starts trading or after the end of the previous accounting period.

How do large companies pay quarterly instalments?

Companies with profits over £1.5 million usually pay Corporation Tax in quarterly instalments. These are typically due 3, 6, 9, and 12 months after the start of the accounting period.

What happens if I pay Corporation Tax late?

Late payment of Corporation Tax incurs interest on the unpaid amount. Repeated or significant delays may result in additional penalties on top of interest.

Where can I find my Corporation Tax payment reference?

Your 17-character Corporation Tax payment reference is shown on HMRC’s notice to file and within your HMRC online Corporation Tax account. Always include it when making payments to ensure correct allocation.

When is Corporation Tax Due?

A complete, accountant-written guide covering corporation tax deadlines, payment rules, filing dates, penalties, interest charges, and how to avoid costly mistakes.

Ragdoll cat with green eyes and white fur sat on the edge of a chais lounge holding a calculator.

When is my Corporation Tax Due? (UK Guide 2025)

Corporation Tax is one of HMRC’s strictest compliance areas — and missing the deadline can trigger interest, penalties, late-filing fines, payment demands, and even enforcement action.

This guide explains everything you need to know, clearly and practically.

See Limited Company Tax Return Plans

1. What Is the Corporation Tax Deadline?

Corporation Tax payment deadline:

9 months and 1 day after the end of your accounting period.

CT600 filing deadline:

12 months after the end of your accounting period.

These are two separate deadlines — and HMRC expects payment before the CT600 is filed.

Example

If your accounting year ends on 31 March 2025:

Corporation Tax payment due: 1 January 2026
CT600 filing deadline: 31 March 2026

2. Corporation Tax Payment Deadlines Explained

A) Small and medium companies (most UK companies)

You must pay all Corporation Tax within 9 months and 1 day after your year end.

B) Large companies (profits > £1.5m)

You may need to pay in quarterly instalments, usually starting 7 months into the accounting year.

C) Very large companies (profits > £20m)

Payments may be due as early as 3 months after the start of the accounting period.

If you’re unsure which regime applies, we can confirm this for you.

3. CT600 Filing Deadline (Corporation Tax Return)

Your Corporation Tax return (CT600) must be filed:

Within 12 months of your accounting period end.
Submitted digitally via HMRC’s online service or approved software.

Important

Even if your company made no profit or is dormant, you may still need to submit a CT600 if HMRC issued a “Notice to Deliver a Company Tax Return”.

4. How to Pay Corporation Tax

Choose a method that suits you — always include your **Corporation Tax payment reference** (your 17-character CT reference) so HMRC can allocate the payment correctly.

Method	Typical processing time	Notes / best practice
Faster Payments	Same working day (often instant)	Fast and recommended. Use the 17-character CT payment reference. Check with bank daily cut-off times.
CHAPS	Same working day (by bank cut-off)	Same-day guaranteed settlement — bank CHAPS fees may apply. Send proof of payment if HMRC query arises.
BACS (bank transfer)	Usually 1–3 working days	Allow extra time before the deadline — use Faster Payments / CHAPS if close to due date.
Direct Debit	Usually 3–5 working days to set up	Only use if set up well ahead of payment date. Can be convenient for repeat liabilities.
Debit/Credit card (HMRC online)	Immediate	Instant confirmation. Note: HMRC may charge a small fee for card payments.
Paying from outside the UK	Varies — allow several working days	Use HMRC’s international bank details and include your CT payment reference. Check foreign transfer cut-off times and FX fees.

Always use your 17-character CT payment reference (not your UTR) — this is shown on HMRC notices and your online corporation tax account.
If you are close to the deadline, prefer Faster Payments or CHAPS to avoid late payment interest.
Keep proof of payment (bank screenshot / CHAPS confirmation) for at least 6 years in case HMRC queries allocation.
If you cannot pay on time contact HMRC immediately to discuss a Time to Pay arrangement — interest will still apply but penalties may be mitigated.

5. What Happens if You Miss the Corporation Tax Deadline?

Missing the payment deadline triggers interest from day one, and late filing may trigger automatic penalties. Below is a detailed breakdown.

A) Late Payment Consequences

1. Interest on Late Payment

HMRC charges late-payment interest daily until the tax is fully settled. The rate changes periodically (based on the Bank of England base rate).

Key points:

Interest is not negotiable.
Interest applies even if your CT600 is not yet filed.
HMRC will not pause interest if you dispute the amount.

2. Penalties for Failure to Notify Chargeability

If you had taxable profits but did not tell HMRC that you needed to file a return, penalties can range from:

Non-deliberate: up to 30% of the unpaid tax
Deliberate: up to 70%
Deliberate and concealed: up to 100%

B) Late Filing Penalties (CT600)

HMRC applies automatic penalties for late CT600 returns. The table below summarises the standard penalty steps.

Delay after filing deadline	Penalty (standard)	What happens / notes
1 day late	£100	Automatic fixed penalty for small delay.
3 months late	Additional £100	Further fixed penalty added on top of the initial £100.
6 months late	Estimate-based penalty or 10% of unpaid tax	HMRC may estimate your tax and add a 10% surcharge.
12 months late	Further 10% surcharge	Another 10% surcharge applied if unaddressed.
Repeated late filings	Up to £500 per repeat	Fixed fines rise to £500 for repeated non‑compliance.

Appeals & reasonable excuse

You can ask HMRC to cancel or reduce penalties if you have a reasonable excuse such as illness, system failure or events outside your control — always supply evidence.

C) Enforcement Action

If the company continues to ignore payment requests, HMRC may escalate to:

Debt collectors
Penalty notices
Charging orders
Freezing bank accounts
Compulsory liquidation (extreme cases)

These scenarios are rare — but only when companies communicate early.

6. Can You Request Extra Time to Pay or File?

Yes — but it must be handled correctly.

A) Requesting More Time to Pay (Time to Pay Arrangement)

HMRC may agree to a Time to Pay (TTP) arrangement if:

You contact them before or immediately after the deadline.
Your company is temporarily unable to pay.
You can demonstrate the ability to clear the debt over time.

What HMRC usually requires:

Latest company accounts
Cashflow forecast
Explanation of financial difficulty
Realistic repayment proposal

A typical arrangement lasts 6–12 months, but can be longer in justified cases.

Key benefit:
Late-payment penalties may be avoided — although interest still applies.

B) Requesting More Time to File the CT600

Extensions to file are rare and granted only where a company can show:

Circumstances outside its control (e.g., severe illness, system failure, loss of records).
Evidence of attempts to comply.

HMRC does not usually accept:

Being busy
Your accountant being unavailable
Missing records due to poor record-keeping

If granted, late-filing penalties can be removed.

7. How to Avoid Corporation Tax Penalties (Proactive Strategies)

1. Use cloud accounting software

Systems like Xero, FreeAgent, and QuickBooks help ensure:

Accurate bookkeeping
On-time VAT and payroll submissions
Real-time profit estimates to forecast CT liability

2. Conduct year-end tax planning early

Activities such as:

Claiming capital allowances
Reviewing director salaries and dividends
Optimising pension contributions
Utilising losses effectively

...all help ensure you know your expected Corporation Tax bill well ahead of time.

3. Set aside Corporation Tax monthly

A common method:

Transfer 19%–25% of monthly profit to a separate tax savings account.

4. File early

Many companies now file CT600s months before the deadline, giving peace of mind and time to plan the payment.

5. Maintain a reminders system

Use:

Accounting software alerts
Google Calendar
HMRC email reminders
Your accountant’s compliance calendar

6. Have your accountant run pre-year-end reviews

This ensures estimated tax is forecast accurately and ahead of time.

8. Common Questions About Corporation Tax Deadlines

1. Can I pay Corporation Tax early?

Yes — HMRC will credit the balance to your Corporation Tax account.

2. What if my company is dormant?

You may still receive a “Notice to File”, and if you do, you must submit a CT600 even if no tax is due.

3. What if I miss the deadline by accident?

You should:

Pay the outstanding tax immediately.
File your CT600 as soon as possible.
Contact HMRC if you cannot pay in full.
Ask your accountant to request penalty mitigation where appropriate.

4. Can penalties be removed?

Yes — HMRC can reduce penalties if you have a reasonable excuse, such as:

Serious illness
Bereavement
System failures
Events outside your control

9. Summary: Key Corporation Tax Deadlines

Keep these key deadlines in mind to avoid late filing or payment penalties.

Requirement	Deadline
Pay Corporation Tax	9 months + 1 day after year end
File CT600 return	12 months after year end
Tell HMRC your company is active for tax	When you start trading
Quarterly instalments (large companies)	As early as 3–7 months into year

10. Need Specialist Help With Corporation Tax?

We manage corporation tax compliance for UK companies of all sizes, ensuring:

Returns are filed correctly
Deadlines are never missed
Allowances and reliefs are maximised
Risks of penalties and HMRC inquiries are minimised
Clear forecasting of upcoming tax bills
Full support in negotiating with HMRC