Late Corporation Tax can become expensive surprisingly quickly. A company may have to deal with the original tax bill, late-payment interest, late-filing penalties and, in serious cases, additional tax-related penalties. The first thing to understand is that late payment and late filing are different problems. A company can pay its Corporation Tax on time but file its Company Tax Return late, or file on time but fail to pay the tax by the payment deadline. Each situation has different consequences.

For most companies with taxable profits of up to £1.5 million, Corporation Tax is normally due 9 months and 1 day after the end of the accounting period, while the Company Tax Return is normally due 12 months after the end of that accounting period. This guide explains how late Corporation Tax penalties work, what can trigger them, how the rules have changed, and what to do if your company has already missed a deadline.

What Is a Late Corporation Tax Penalty?

A late Corporation Tax penalty is a charge imposed by HM Revenue & Customs (HMRC) when a company fails to meet certain Corporation Tax obligations. There are two situations that are particularly important:

• Late payment of Corporation Tax
• Late filing of the Company Tax Return

They should not be confused with each other. If a company pays its tax late, HMRC generally charges late-payment interest from the day after the tax was due until it is paid. If the company files its tax return late, it can receive a separate late-filing penalty. In other words, paying the tax does not automatically remove a filing penalty, and filing the return does not automatically settle the tax bill.

When Is Corporation Tax Due?

For companies with taxable profits of up to £1.5 million, Corporation Tax is generally due 9 months and 1 day after the end of the accounting period. The Company Tax Return normally has a later deadline: 12 months after the end of the accounting period.

Example

Suppose a company has an accounting period ending on 31 December 2026. Its Corporation Tax would normally be due on: 1 October 2027, Its Company Tax Return would normally be due on: 31 December 2027, That means the company may have to pay its estimated Corporation Tax before it submits the final tax return. This is one of the most common points of confusion for new company directors.

Large companies have different payment rules

Companies with annual taxable profits above £1.5 million may have to pay Corporation Tax in instalments rather than making one payment 9 months and 1 day after the accounting period ends. Different rules apply depending on profit levels, accounting periods and group circumstances.

What Happens If You Pay Corporation Tax Late?

If Corporation Tax is paid after its deadline, HMRC generally charges late-payment interest. The interest runs from the day after the tax was due until the date the outstanding amount is paid. This is important because late payment does not necessarily begin with a large fixed penalty. The immediate financial consequence can be interest accumulating on the unpaid tax. The longer the debt remains unpaid, the greater the cost can become. A company should therefore avoid thinking:

"We'll pay it when we have the cash."

If cash flow is becoming a problem, it is better to address the situation early and discuss the position with HMRC where appropriate.

What Happens If You File the Company Tax Return Late?

Late filing is a separate issue. For Company Tax Returns with a filing date on or after 1 April 2026, the fixed late-filing penalties increased. The current structure is:

The higher penalties apply where the company has been liable to penalties for the preceding two consecutive accounting periods and continues to file late. This represents a significant change from the previous £100/£200 structure.

A key point for 2026

If you are reading older articles about Corporation Tax penalties, check their publication date carefully. Some older guidance still describes the previous £100 and £200 penalties. The fixed penalties increased for Company Tax Returns with filing dates on or after 1 April 2026. That distinction is particularly important when researching the penalty attached to a current filing.

Can You Be Penalised If Your Company Owes No Corporation Tax?

Yes. A company can receive a late-filing penalty even if it has no Corporation Tax to pay. HMRC explicitly states that a Company Tax Return is still required where the company makes a loss or has no Corporation Tax to pay, if HMRC has issued a notice to deliver a return. This catches some new founders off guard. For example, imagine a startup that:

• was incorporated during the year;
• spent money developing its product;
• generated no revenue;
• made a trading loss; and
• therefore owes no Corporation Tax.

The directors may assume there is nothing to file. That assumption can be wrong. If the company is required to submit a Company Tax Return and misses the filing deadline, it can still receive a penalty.

What If the Return Is Six Months Late?

The consequences become more serious as the delay continues. Under the current rules, a tax-related penalty can arise when the Company Tax Return remains outstanding beyond the relevant 18-month point. The tax-related penalty is generally:

• 10% of unpaid tax where the return is delivered within two years of the end of the accounting period; or
• 20% of unpaid tax in other cases.

This is separate from the fixed late-filing penalties. The practical message is straightforward: do not allow an overdue return to sit unresolved for months simply because the initial penalty seems manageable.

What Is a Corporation Tax Determination?

If a Company Tax Return becomes significantly overdue, HMRC may estimate the company's Corporation Tax liability. This is called a tax determination. HMRC's current guidance states that if a return is more than six months late, it may issue a determination estimating the Corporation Tax the company should pay. The company still needs to submit its actual Company Tax Return. Once the return is filed, HMRC can recalculate the company's actual tax, interest and penalties. A determination should therefore not be treated as a substitute for filing the return.

What If Your Accountant Missed the Deadline?

This is one of the most common explanations given by directors. Perhaps the company sent its accounts and records to an accountant in good time, but the accountant failed to submit the Company Tax Return. That does not automatically mean the penalty disappears.

The company remains responsible for its tax compliance, even when an accountant or other professional is handling the filing. However, the circumstances can matter when considering whether there was a reasonable excuse. The better approach is to establish exactly what happened:

• When did you provide the information?
• Did you give the accountant enough time?
• Did you follow up?
• Were there communication problems?
• When did you discover the return had not been filed?
• How quickly did you take corrective action?

If the company has received a penalty, preserve relevant emails, engagement letters, invoices and correspondence. They may help establish the facts if an appeal is appropriate.

Can You Appeal a Late Corporation Tax Penalty?

Yes, a company can appeal a late-filing penalty if it believes the penalty is wrong or it had a reasonable excuse. HMRC allows appeals against late Company Tax Return penalties where appropriate. The company should normally file the outstanding return before appealing. A successful appeal is not simply about saying:

"There was a problem."

You need to explain what happened and why it prevented the company from complying with the deadline.

What can count as a reasonable excuse?

The circumstances must be considered individually, but examples can include serious and unexpected events that genuinely prevented compliance. The strength of an appeal usually depends on three things:

1. The seriousness of the circumstances
2. The connection between those circumstances and the missed deadline
3. How quickly the company acted once the problem was resolved

Evidence can make a substantial difference. For example, if an unexpected event genuinely prevented the director or responsible person from dealing with the company's tax affairs, supporting documentation can help establish the timeline.

What Should You Do If You Have Already Missed the Deadline?

Don't wait for the penalty notice before taking action. Use this sequence.

1. File the overdue return

If the Company Tax Return is outstanding, get it submitted as soon as possible. HMRC specifically recommends filing and paying first to avoid further penalties where possible.

2. Calculate the Corporation Tax position

Determine whether the company owes Corporation Tax and how much. Do not assume that a late return automatically means the company owes tax, or that no tax is due simply because the business has made little revenue.

3. Pay what you can

If the tax is due and the company has the funds, paying promptly limits the period over which late-payment interest can accrue.

4. Check the penalty notice

Look at:

• the accounting period;
• filing deadline;
• date the return was received;
• penalty amount;
• date of the penalty notice; and
• HMRC's instructions for payment or appeal.

5. Consider an appeal

If you believe there was a reasonable excuse or HMRC has made an error, consider appealing under the applicable procedure. Do not miss the appeal deadline while trying to resolve the underlying tax issue.

Late Filing vs Late Payment: A Simple Example

Imagine a company has:

• Corporation Tax due: £8,000
• Tax payment deadline: 1 October
• Company Tax Return deadline: 31 December

The company does neither. By 1 October, the £8,000 becomes overdue and late-payment interest can begin to accrue. If the company then misses the 31 December filing deadline, it can also face a late-filing penalty. If the return remains outstanding for much longer, further tax-related consequences may arise. So one missed accounting deadline can create several separate costs. This is why directors should track payment and filing dates independently.

Does Paying the Tax Remove the Late Filing Penalty?

No, not automatically. Suppose the company pays all of its Corporation Tax on time but submits its Company Tax Return two months late. The company can still receive a late-filing penalty because filing and payment are separate obligations. Likewise, filing the return on time does not prevent interest arising if the Corporation Tax itself was paid late. This is one of the simplest, and most important, Corporation Tax compliance rules to remember.

What If the Company Cannot Afford the Tax?

Cash-flow problems can make Corporation Tax particularly difficult for early-stage businesses. A company may have generated accounting profit but have limited cash available because money has been reinvested into stock, equipment, staff, marketing or expansion. Lack of funds does not automatically provide a reasonable excuse for failing to pay tax.

If the company cannot pay, it should deal with the situation proactively rather than allowing the debt to grow unnoticed. Depending on the circumstances, HMRC may be able to discuss a Time to Pay arrangement. The important point is to contact HMRC before the situation becomes significantly worse.

Corporation Tax Penalties for Startups

Startups are particularly vulnerable to late Corporation Tax problems because their first accounting period can be confusing. A new company may have:

• a short first accounting period;
• separate Companies House and HMRC deadlines;
• no revenue;
• several months of setup expenditure;
• overseas founders;
• an outsourced accountant; or
• directors unfamiliar with UK tax administration.

A founder living outside the UK may also mistakenly assume that because the company operates primarily online, its UK filing obligations are less important. They are not. The company's UK tax obligations continue regardless of where the founders happen to live.

For international founders using a UK company formation and management platform such as IncorpUK, maintaining a clear calendar of Companies House and HMRC obligations is particularly important because these are separate compliance systems.

How to Prevent Late Corporation Tax Penalties

The best penalty is the one you never receive.

Maintain a compliance calendar

Record at least:

• accounting period end date;
• Corporation Tax payment deadline;
• Company Tax Return deadline;
• Companies House accounts deadline;
• confirmation statement deadline;
• VAT deadlines, if applicable;
• PAYE deadlines, if applicable.

Don't rely on one reminder

Use several reminders before each important deadline. For example:

• 60 days before: begin preparation
• 30 days before: review records
• 14 days before: finalise figures
• 3 days before: confirm filing/payment

Confirm that filings were actually submitted

If an accountant handles the return, ask for confirmation that it has been successfully submitted. Don't confuse "your accounts are ready" with "HMRC has received the Company Tax Return."

Keep money aside for Corporation Tax

A tax reserve can prevent a profitable company from becoming a late payer simply because its cash has been spent elsewhere.

Frequently Asked Questions

How much is a late Corporation Tax penalty?

For Company Tax Returns with filing dates on or after 1 April 2026, the standard fixed penalty is £200 when filed within three months late and £400 when filed more than three months late. Repeated late filing can increase these penalties to £1,000 and £2,000 respectively. Additional tax-related penalties can apply in prolonged cases.

Is Corporation Tax due before the tax return?

Usually, yes. For companies with taxable profits up to £1.5 million, Corporation Tax is normally due 9 months and 1 day after the accounting period ends, while the Company Tax Return is normally due 12 months after the accounting period ends.

Can I get a late Corporation Tax penalty if my company made a loss?

Yes. A company may still have to submit a Company Tax Return even if it made a loss or has no Corporation Tax to pay, and late filing can result in a penalty.

Does HMRC charge interest on late Corporation Tax?

Yes. HMRC charges late-payment interest on Corporation Tax that is paid late or remains underpaid. Interest normally runs from the day after the payment deadline until the tax is paid.

Can I appeal a late Corporation Tax penalty?

Yes. A company can appeal where appropriate, including where it believes it had a reasonable excuse or the penalty is otherwise incorrect. HMRC generally expects the outstanding Company Tax Return to be filed before the appeal is considered.

Does an accountant's mistake automatically cancel the penalty?

No. Appointing an accountant does not automatically transfer responsibility for the company's compliance obligations. However, the specific circumstances may be relevant when considering a reasonable-excuse appeal.

What happens if my Corporation Tax return is more than six months late?

HMRC may issue a tax determination estimating the Corporation Tax it believes is due. The company must still submit the actual return, after which HMRC can recalculate the tax, interest and penalties.

Can a company pay Corporation Tax late because it has no cash?

A lack of funds does not automatically excuse late payment. If your company cannot pay, it is better to contact HMRC promptly and investigate available payment arrangements rather than simply allowing the debt to accumulate.

Are Companies House penalties and HMRC penalties the same?

No. Companies House and HMRC are separate authorities with different filing obligations and penalty systems. A company can therefore be compliant with one authority while being overdue with the other.

Conclusion

Late Corporation Tax penalties are best understood as part of a wider compliance system rather than as a single charge. For most companies, the two deadlines to remember are straightforward: pay Corporation Tax on time and file the Company Tax Return on time. They are separate obligations, and missing either can have financial consequences.

The rules have also changed. From 1 April 2026, fixed late-filing penalties for relevant Company Tax Returns increased, making repeated or prolonged filing failures more expensive. If your company has already missed a deadline, act rather than wait. File the outstanding return, establish the tax liability, pay what is due where possible, check the penalty notice and consider an appeal if there is a genuine basis for doing so.

For founders, especially those running UK companies from overseas, the safest approach is simple: know your dates, separate tax payments from tax filings, keep accurate records and make someone clearly responsible for each obligation. A few minutes spent maintaining that system can prevent hundreds or thousands of pounds in avoidable costs.