If you are running a limited company in the UK, it can bring immense flexibility. However, you must understand that it also comes with more tax and other financial responsibilities. That’s right, you are responsible for handling your own taxes.
Unlike PAYE Income Tax, Corporation Tax is generally self-assessed by the company. The company is responsible for calculating its taxable profits and Corporation Tax liability, filing its Company Tax Return and paying any tax due by the relevant deadline. But how to calculate small business Corporation Tax?
This article explains how to calculate corporation tax for small businesses, so you are prepared financially to carry out your responsibilities with confidence. It also explains how a small business Corporation Tax calculator can provide an initial estimate. However, the final liability may require adjustments for tax rules, reliefs, capital allowances, associated companies and other circumstances.
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What is Small Business Corporation Tax?
Corporation Tax is a tax that most active limited companies pay on their taxable profits. You pay this tax regardless of your business size. Taxable profits can include adjusted trading profits, chargeable gains and certain types of investment income, depending on the company’s circumstances.
Moreover, it is self-assessed, meaning the company has to calculate and pay what it owes to HMRC. This makes it even more important to understand how you can calculate small business Corporation Tax.
What are the UK Corporation Tax Rates for 2026/27?
The UK has two main Corporation Tax rates based on your company’s taxable profits:
Small Profits Rate
Small Profits Rate, which is 19%, applies to companies with profits under £50,000.
Main Rate
The main rate is 25% and applies to companies with profits over £ 250,000, subject to the rules for associated companies and shorter accounting periods.
Note: A company with profits between £50,000 and £250,000 may qualify for Marginal Relief.
What is Corporation Tax Marginal Relief?
Understanding Marginal Relief is a part of Corporation Tax and can help you calculate small business Corporation Tax. A company may qualify for Marginal Relief where its taxable profits fall between the relevant lower and upper limits. Marginal Relief reduces the Corporation Tax liability that would otherwise arise under the 25% Main Rate.
Additionally, you may be able to claim Marginal Relief if your company’s taxable profits are between £50,000 and £250,000. These limits are reduced proportionately if the company has associated companies, or if the accounting period is shorter than 12 months, subject to the relevant Corporation Tax rules.
How to Calculate Small Business Corporation Tax?
To estimate corporation tax for small businesses, you need to work out your company’s taxable profits and apply the relevant Corporation Tax rules. In addition to taxable profits and tax rules, you also need to consider any allowable expenses and tax reliefs that may reduce your taxable profits.
Follow these practical steps to estimate small business Corporation Tax:
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Determine Your Total Income
Start with your company’s accounting profit and make the relevant Corporation Tax adjustments. These can include adding back expenses that are not deductible for Corporation Tax purposes and deducting applicable tax reliefs or capital allowances. The resulting taxable profit is then used to determine the Corporation Tax liability.
Let’s assume the company has £300,000 of sales and £100 of relevant interest income. These figures form part of the company’s income. But the Corporation Tax calculation must then take account of deductible expenses, tax adjustments and the applicable rules for different types of income.
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Identify Your Corporation Tax Rate
For a 12-month accounting period, the 19% Small Profits Rate generally applies to taxable profits of £50,000 or less, while the 25% Main Rate generally applies to taxable profits of £250,000 or more. Companies with profits between these limits may qualify for Marginal Relief. The thresholds can be affected by associated companies and shorter accounting periods.
You can check official HMRC guidance and detailed thresholds, as it will help you calculate small business Corporation Tax with ease.
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Key Deadlines to Remember
Remember the essential deadlines for Corporation Tax. Pay any tax due 9 months and 1 day after your accounting period ends.
Moreover, file your Company Tax Return (Form CT600) 12 months after your accounting period ends.
Example of Calculating Corporation Tax on £40,000 Profit
Suppose your company has £40,000 of taxable profits for a 12-month accounting period and has no associated companies. Since the taxable profits are under £50,000, the 19% small profits rate applies.
£40,000 × 19% = £7,600
Therefore, your company’s Corporation Tax liability would be £7,600, assuming there are no other relevant adjustments or special rules.
Example of Calculating Corporation Tax on £100,000 Profit
Here is another example to learn how you can calculate small business Corporation Tax on £100,000 profit. Keep in mind that the calculation can be more complicated when taxable profits are between £50,000 and £250,000, as Marginal Relief may apply.
Assume your company has taxable profits of £100,000, a 12-month accounting period, and no associated companies. Your company falls within the Marginal Relief range. So, you do not simply pay 25% on profits, nor do you pay 19% on the whole amount.
Instead, Corporation Tax is calculated using the Marginal Relief rules, which take your company’s augmented profits, applicable limits, and taxable total profits into account.
You can use a small business Corporation Tax calculator to find out how much corporation tax your company will be liable for.
Let’s understand in another way: £100,000 of taxable profits
For a 12-month accounting period with no associated companies, £100,000 of taxable profits falls within the Marginal Relief range. The company does not simply multiply £100,000 by 19% or 25%. Instead, the Corporation Tax liability is calculated using the Marginal Relief rules, which take account of the lower and upper limits and the company’s augmented profits. The exact calculation can differ where exempt distributions or other relevant factors apply.
When is the Corporation Tax Deadline?
Although there is no official deadline to calculate small business Corporation Tax, it is best to estimate as early as possible. However, there is a deadline for filing and paying Corporation Tax.
Normally, Corporation Tax is due 9 months and 1 day after the end of the accounting period. However, the Corporation Tax Return (CT600) is due 12 months after the end of the accounting period.
Most people often confuse the Corporation Tax deadline. Let’s understand it with an example. So, if your accounting period ends on 31 December 2026, your Corporation Tax would typically be due by 1 October 2027. Additionally, the Company Tax Return would be due by 31 December 2027.
Do You Pay Corporation Tax on a Limited Company?
Yes, you must pay Corporation Tax on all your taxable profits, including trading profits, investment profits, and chargeable gains from selling business assets.
Remember, you do not automatically register for Corporation Tax when you set up your company. You must tell HMRC that your company is liable for Corporation Tax.
How to Calculate Corporation Tax for a Limited Company?
To calculate small business Corporation Tax for a UK limited company, apply the correct tax rate to the taxable profits. Follow the step-by-step calculation guide:
- Calculate accounting profit
- Identify non-deductible expenses and make tax adjustments
- Apply capital allowances where applicable
- Calculate taxable total profits
- Check whether Marginal Relief applies
- Apply the relevant Corporation Tax calculation
- Calculate the final liability
How to Pay Corporation Tax?
Once you calculate small business corporation tax, you must pay the tax by the deadline.
You can pay Corporation Tax using HMRC’s available electronic payment methods, such as through your online bank accounts, by Faster Payments or CHAPS, or a debit or corporate credit card.
Processing time depends on your payment method. Always check HMRC’s current payment guidance for the latest payment methods and processing times. Also, make sure you pay the tax you owe to HMRC by the deadline. It may charge you interest if you do not pay on time.
Do Allowable Expenses Affect Corporation Tax?
Yes, allowable business expenses can reduce the taxable profit on which Corporation Tax is calculated.
HMRC differentiates between capital expenditure and revenue expenses. When calculating taxable profits, revenue expenses may be deductible if they meet the relevant conditions. However, capital expenditure is usually dealt with separately through capital allowances where applicable.
What Business Expenses Can Reduce Corporation Tax?
Understanding allowable expenses allows you to calculate small business corporation tax accurately and avoid overpaying.
Here are the allowable Corporation Tax allowances that help you reduce your taxable profit and final tax liability.
- Employee wages and certain staff costs;
- Professional fees;
- Business loan interest;
- Certain insurance costs;
- Business running costs; and
- Other revenue expenses incurred wholly and exclusively for the business.
Keep in mind that not every business expense is deductible. You must claim legitimate business expenses and calculate small business corporation tax accurately to avoid any errors.
What if You Can’t Pay Your Corporation Tax Bill?
After a careful small company Corporation Tax calculation, you may think that you cannot pay your Corporation Tax bill. So what happens then?
If you cannot pay your tax bill on time, you can contact HMRC. Depending on your circumstances, you may be able to arrange a Time to Pay agreement to spread the payments over an agreed period.
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Final Thoughts
Knowing how to calculate small business Corporation Tax can help you determine your company’s tax bill and avoid unexpected costs. However, you must calculate your Corporation Tax accurately to avoid any errors or penalties.
You need to calculate your taxable profits, consider allowable expenses and capital allowances, and determine whether Marginal Relief applies. If you are overwhelmed with your Corporation Tax and need help calculating it, we are here to help.
At CAIL, we have a team of qualified accountants who can help you calculate your Corporation Tax, identify available tax reliefs, and ensure you file on time. Moreover, if you need advice on Corporation Tax or what you need to pay, get in touch with our experts.
Disclaimer: This article intends to provide general information on calculating small business corporation tax.