Corporation Tax in the UK: A Guide for Businesses

corporation tax

IN THIS ARTICLE

Compliance with UK corporation tax regulations helps businesses optimise financial strategies while avoiding penalties and legal issues.

The UK’s tax landscape is characterised by a range of reliefs, incentives, and compliance requirements that businesses must navigate to minimise tax liabilities and avoid penalties. While the tax rates and rules can seem daunting, understanding the underlying principles and staying informed about legislative changes can provide significant financial benefits.

This guide provides a comprehensive overview of corporation tax in the UK, covering the basics of what corporation tax is, who needs to pay it, and how to calculate your company’s tax bill. We also look at how to file your company tax return (CT600), the deadlines involved, and the reliefs potentially available to reduce your tax liability.

 

 

Section A: What is Corporation Tax?

 

Corporation tax is a mandatory tax imposed on the profits earned by companies and certain types of organisations. It is a significant source of government revenue in the UK and plays a vital role in the country’s economic landscape.

 

1. Definition and Explanation of Corporation Tax

 

Corporation tax is a tax levied on the profits of companies and organisations. This includes profits from trading, investments, and the sale of assets.

All UK-based companies, as well as foreign companies with a UK branch or office, are subject to corporation tax. The rate of corporation tax is set by the government and can vary depending on the level of profit and company size.

The primary components of corporation tax include:

a. Trading Profits: Income from the company’s primary business activities.
b. Investment Income: Earnings from investments such as dividends and interest.
c. Capital Gains: Profits from the sale of company assets.

Note: Depreciation is not deductible for corporation tax purposes. Instead, businesses claim capital allowances to obtain tax relief for qualifying asset expenditure.

 

2. Differences Between Corporation Tax and Other Forms of Business Taxation

 

Corporation tax is distinct from other types of business taxes, such as:

a. Income Tax: Paid by individuals and sole traders on their personal income.
b. Value Added Tax (VAT): A consumption tax levied on goods and services.
c. National Insurance Contributions (NICs): Paid by employers and employees to fund state benefits.

Unlike income tax, which is paid by individuals and self-employed persons on their earnings, corporation tax is specifically aimed at corporate entities. VAT is a tax on the value added to goods and services and is ultimately borne by the consumer, not the business. NICs support social welfare programmes and are not directly related to company profits.

 

3. How Corporation Tax Differs in the UK from Other Countries

 

The UK’s approach to corporation tax has unique characteristics shaped by its economic history, government policies, and fiscal philosophy. Here’s how it compares to other countries:

AspectDetails
Tax Rates and StructureThe UK has a competitive corporation tax rate compared to many other developed countries. Since April 2023, the standard rate is 25%, with reduced rates for smaller profits. This balance is designed to attract foreign investment and stimulate domestic growth.
Historical ContextThe UK’s corporation tax system has evolved significantly since its introduction in 1965. Initially, the tax rate was relatively high, but successive governments have reduced it to encourage business activity and international competitiveness.
Philosophy and ReasoningThe UK’s philosophy balances raising government revenue with fostering a business-friendly environment. The tax structure is designed to ensure businesses contribute fairly while retaining profits for reinvestment and growth.
Tax Reliefs and IncentivesThe UK offers a wide range of reliefs and incentives, such as Research and Development (R&D) relief (moved to a merged scheme in 2024) and capital allowances, to support innovation and investment.
Compliance and AdministrationThe UK’s tax administration is known for its rigour, with a comprehensive legal framework and guidance from HMRC. This clarity helps businesses meet obligations effectively.
International ComparisonsFor example, the United States has a federal corporation tax rate supplemented by state taxes, often resulting in a higher overall burden. Ireland offers a lower rate to attract multinationals. The OECD’s global minimum tax reforms (Pillar 2, 15% effective rate) may also shape cross-border tax competitiveness.

Section A Summary: Corporation tax is the UK’s principal tax on company profits, applying to UK companies and foreign entities with UK operations. It differs from income tax, VAT, and NICs by focusing on business profits. The UK balances competitive rates with targeted reliefs and a rigorous compliance framework.

 

 

Section B: Corporation Tax Rates in the UK

 

As of the latest fiscal year, the standard corporation tax rate in the UK is 25%, applying to the profits of most companies. There is a small profits rate of 19% for companies with profits of £50,000 or less. For profits between £50,001 and £250,000, marginal relief applies, gradually increasing the effective rate from 19% to 25%.

Important: These thresholds must be adjusted for associated companies and also for short accounting periods. For example, if a company has two associated companies, the £50,000 threshold reduces to £16,667.

 

Profits RangeTax RateDescription
£0 – £50,000 (adjusted for associated companies/periods)19%Small profits rate
£50,001 – £250,000 (adjusted)Marginal ReliefGradual increase from 19% to 25%
Over £250,000 (adjusted)25%Main corporation tax rate

 

1. Historical Context and Recent Changes

 

The corporation tax rate has changed significantly since 1965. The general trend has been downward, until the recent April 2023 rise back to 25%.

Year/PeriodTax RateNotes
196540%Corporation tax introduced.
1980s35%Progressive reductions to encourage business activity.
1990s30%Further cuts under Conservative governments.
200828%Reduced during the financial crisis.
2010–201520%Coalition government staged cuts to 20%.
201719%Held at 19% until April 2023.
April 202325% (tiered system)Main rate reintroduced, with small profits rate and marginal relief.

 

2. Potential Future Changes

 

The Labour government elected in July 2024 has stated it will not raise corporation tax above 25%, but will keep rates under review depending on economic conditions. Internationally, the OECD Pillar 2 global minimum tax of 15% is being implemented, although the UK’s rate already exceeds this.

 

Example: A company with taxable profits of £100,000 and no associated companies will benefit from marginal relief, giving an effective tax rate of around 21.5%, rather than a flat 25%.

 

Section B Summary: The UK now applies a tiered corporation tax system with a 25% main rate, 19% small profits rate, and marginal relief in between. Associated company rules and accounting period length directly affect thresholds. While the current government has committed not to increase rates further, businesses must monitor policy and global reforms for future changes.

 

 

Section C: Who Pays Corporation Tax?

 

Corporation tax is levied on the profits of organisations operating in the UK. Liability depends on whether the entity is incorporated in the UK, has a UK branch, or carries out taxable activities here.

 

1. Organisations Liable to Pay Corporation Tax

 

The following are required to pay corporation tax:

a. UK-Resident Companies: Companies incorporated in the UK are subject to corporation tax on worldwide profits, including trading income, investments, and capital gains.
b. Foreign Companies with a UK Branch or Office: Overseas companies with a permanent establishment in the UK pay corporation tax on profits attributable to UK activities.
c. Certain Other Organisations: Non-company entities such as housing associations, co-operatives, clubs, and societies may also be subject to corporation tax if they trade and generate profits.
d. Charities: Exempt on most income and gains used for charitable purposes, but non-charitable trading activities may still be taxable.

 

2. Examples of Different Business Structures

 

a. Private Limited Companies (Ltd): The most common form of incorporated entity. Profits are fully subject to corporation tax.
b. Public Limited Companies (PLC): Larger companies that can list shares publicly. Their profits are taxed under the same rules.
c. Foreign Companies with a UK Branch: For example, a US tech firm opening an R&D centre in Manchester must pay UK corporation tax on the branch’s profits.
d. Clubs and Societies: A golf club running a profitable clubhouse bar is liable on trading income.
e. Housing Associations: Charitable housing associations are generally exempt, but profits from non-charitable commercial ventures may be taxed.
f. Co-operatives and Friendly Societies: Member-owned entities can fall within the charge if they trade and generate taxable profits.

 

Example: A French retailer opening shops in London pays UK corporation tax on the UK store profits, but its French operations remain taxed in France.

 

Section C Summary: Corporation tax applies broadly to UK-incorporated companies, overseas businesses with UK branches, and certain non-company organisations. Charities are generally exempt but may be taxed on non-charitable activities. Directors must understand their organisation’s structure to identify corporation tax obligations correctly.

 

 

Section D: How to Calculate Corporation Tax

 

Corporation tax operates on a self-assessment basis. Companies are responsible for calculating, reporting, and paying their liability. Accurate records and proper adjustments are essential to avoid penalties, interest, and HMRC scrutiny.

 

1. Step-by-Step Guide on Calculating Taxable Profits

 

Step 1: Determine Your Accounting Period
Corporation tax is assessed by reference to a company’s accounting period, usually 12 months. The first period may be shorter or longer, requiring two returns if it exceeds 12 months.

Example: A company incorporated on 15 June 2023 prepares first accounts to 30 June 2024. It must file two returns – one for 15 June 2023 to 14 June 2024, and one for 15–30 June 2024.

Step 2: Calculate Gross Profits
Add trading income, investment income, and chargeable gains.

Step 3: Deduct Allowable Expenses
Deduct costs incurred wholly and exclusively for business purposes, excluding disallowables such as client entertaining.

Step 4: Adjust for Capital Allowances
Depreciation is not deductible. Instead, claim capital allowances on plant, machinery, and qualifying equipment.

Step 5: Apply Other Reliefs and Adjustments
Apply eligible reliefs, including:
– Trading loss reliefs (carry-back/forward)
– R&D tax relief (merged scheme from April 2024, or intensive SME regime)
– Group relief
– Patent Box

Step 6: Calculate Taxable Profits
After adjustments, the result is taxable profits.

Step 7: Apply the Corporation Tax Rate
Apply 19%, 25%, or marginal relief as appropriate, considering associated companies and accounting period length.

 

2. Allowable Expenses and Deductions

 

CategoryDescription
Staff CostsSalaries, pensions, benefits
Office CostsRent, utilities, supplies
Travel ExpensesBusiness travel and subsistence
Professional FeesAccounting, legal, consultancy
MarketingAdvertising and promotion
Capital AllowancesRelief on qualifying assets (instead of depreciation)
Loan InterestInterest on business loans (subject to restrictions for large groups)

 

Tip: Expenses must be wholly and exclusively for business. Dual-purpose expenses are usually disallowed.

 

3. Example Calculation

 

DetailAmount (£)
Total Revenue500,000
Allowable Expenses265,000
Capital Allowances25,000
Taxable Profits210,000
Effective Tax Rate~21.5% (marginal relief)
Corporation Tax Liability≈ 45,000

 

Section D Summary: Corporation tax is calculated by identifying income, deducting allowable expenses, applying capital allowances and reliefs, and then using the appropriate tax rate. Depreciation is replaced by capital allowances. Accurate calculations reduce HMRC risks and optimise liabilities.

 

 

Section E: Filing Corporation Tax Returns

 

All UK companies must file an annual corporation tax return using form CT600. The return records the company’s profits, adjustments, and corporation tax liability for the accounting period. Failure to file on time or correctly can lead to penalties, HMRC enquiries, and potential director accountability.

 

1. Filing Deadlines

 

– The CT600 must be filed within 12 months of the end of the accounting period.
– Corporation tax must usually be paid within 9 months and 1 day of the end of the period.

Example: If your accounting period ends on 31 March 2024, the CT600 must be filed by 31 March 2025, and payment made by 1 January 2025.

If the accounting period exceeds 12 months, two returns are required, each with its own filing deadline.

 

2. Registering for Corporation Tax

 

HMRC is notified automatically when a company registers at Companies House. A Unique Taxpayer Reference (UTR) is issued. Companies must register for corporation tax within three months of starting business activities (e.g. trading, renting premises, advertising, hiring staff). Registration is completed online through HMRC’s portal.

 

3. Completing and Submitting the CT600

 

Step 1: Gather Records
Collect financial statements, income, expenses, capital allowances, and relief calculations.

Step 2: Complete the CT600 Main Return
The main CT600 requires company details, taxable profits, reliefs claimed, and the final tax liability.

Step 3: Include Supplementary Pages
Additional schedules may be required, such as:
– CT600A: Loans to participators (close companies)
– CT600B: Charitable donations
– CT600C: Group and consortium relief
– CT600L: R&D expenditure credits (RDEC)
– CT600M/N: Cross-border and international issues

Step 4: File the Return
Most companies must file online using HMRC’s service or commercial software. Paper filing is only allowed in limited cases. The return must be signed or digitally authorised by a director or authorised person.

 

4. Common Errors on the CT600

 

– Using the wrong accounting period dates
– Missing supplementary pages
– Claiming disallowable expenses
– Incorrect capital allowance entries
– Errors in group relief allocations
– R&D entries not updated to reflect 2023–24 scheme changes

 

Section E Summary: Filing the CT600 accurately and on time is a legal requirement. Companies must register within three months of trading, include all necessary supplementary pages, and file within 12 months of year-end. Early preparation, professional oversight, and correct online filing help avoid penalties and HMRC scrutiny.

 

 

Section F: Corporation Tax Payment Deadlines

 

Strict rules govern corporation tax payment deadlines. Missing deadlines results in HMRC charging interest, imposing penalties, and potentially taking enforcement action. Timing depends on company size and profits.

 

1. Standard Payment Deadline

 

Most companies must pay corporation tax within nine months and one day after the end of the accounting period.

Example: If the accounting period ends on 31 March 2024, payment must be made by 1 January 2025.

 

2. Quarterly Instalments for Large and Very Large Companies

 

Companies with annual taxable profits above £1.5 million pay in quarterly instalments. This threshold is reduced by the number of associated companies and by the length of the accounting period if shorter than 12 months.

Quarterly schedule (12-month accounting period):

InstalmentTiming
First6 months and 13 days after the start of the period
Second3 months after the first instalment
Third3 months after the second instalment
Fourth3 months after the third instalment (typically 14 days after the end of the period)

 

For very large companies (profits above £20 million, adjusted for associated companies and accounting period length), payments are earlier, starting 2 months and 13 days into the accounting period.

 

3. Newly Formed Companies

 

New companies may have accounting periods shorter or longer than 12 months. If the first period exceeds 12 months, two returns are required. Payment deadlines remain nine months and one day after each period end.

 

4. Interest and Penalties

 

Interest is charged on late payments from the day after the due date.
Penalties apply for persistent or deliberate late payment.
– Late payment may also jeopardise certain relief claims and group arrangements.

 

5. Practical Compliance Tips

 

– Forecast corporation tax liabilities in advance
– Keep cash reserves aside for expected payments
– Consider paying by Direct Debit to HMRC
– File and pay early where possible
– Large companies should model cash flow for quarterly instalments

 

Section F Summary: Most companies pay corporation tax nine months and one day after year-end, but larger businesses must make quarterly instalments, and very large companies pay even earlier. Associated company rules and accounting period length reduce thresholds. Planning and cashflow management are critical to avoid interest and penalties.

 

 

Section G: Tax Reliefs and Incentives

 

Corporation tax reliefs and incentives provide opportunities to reduce liability. Each has strict eligibility rules, and directors should take advice to ensure compliance and maximise benefits.

 

1. Research and Development (R&D) Tax Relief

 

R&D relief encourages innovation. From April 2024, the system moved to a merged scheme based on the RDEC framework, with a 20% above-the-line credit. Loss-making R&D-intensive SMEs (spending 30% or more on R&D) may claim a more generous repayable credit regime.

 

2. Capital Allowances

 

Capital allowances replace depreciation and provide relief for qualifying investment in assets. Main types include:

Annual Investment Allowance (AIA): 100% relief on expenditure up to £1m per year
Writing Down Allowance (WDA): Percentage-based relief for assets not fully relieved
First-Year Allowance (FYA): 100% relief on specified qualifying assets such as zero-emission vehicles

 

3. Patent Box

 

The Patent Box regime allows profits from patented inventions and qualifying IP rights to be taxed at a reduced 10% rate.

 

4. Creative Industry Reliefs

 

From January 2024, the UK introduced new credits replacing several older reliefs:

Audio-Visual Expenditure Credit (AVEC)
Video Games Expenditure Credit (VGEC)

These provide enhanced tax credits to companies in film, TV, and video games sectors. Older reliefs (e.g. Film Tax Relief, Animation Tax Relief) are being phased out.

 

5. Other Reliefs

 

Group Relief: Losses of one group company can be offset against another’s profits
Loss Carry-Back/Forward: Trading losses can be applied to earlier or later periods, subject to restrictions

 

6. Enterprise Investment Scheme (EIS) and Seed Enterprise Investment Scheme (SEIS)

 

These are investor reliefs, not corporation tax reliefs. They provide income and capital gains tax incentives for investors in early-stage companies, indirectly helping businesses raise equity capital.

 

Section G Summary: Corporation tax reliefs range from R&D and capital allowances to Patent Box and creative sector credits. Each scheme has specific criteria and can reduce liabilities significantly if applied correctly. EIS and SEIS, though not corporation tax reliefs, help attract equity investment. Directors should review reliefs annually to maximise opportunities within HMRC rules.

 

 

Section H: Common Mistakes to Avoid

 

Corporation tax is complex, and errors can result in penalties, missed savings, or HMRC scrutiny. Awareness of common pitfalls helps directors strengthen compliance and governance.

 

1. Frequent Errors with Corporation Tax

 

a. Missing Deadlines: Late CT600 filings or tax payments automatically trigger penalties and interest.
b. Incorrect Profit Calculations: Errors often arise from disallowable expenses, missed capital allowances, or misapplied reliefs.
c. Overlooking Reliefs: Opportunities such as R&D credits, Patent Box, or group relief are often missed.
d. Poor Record Keeping: Inadequate documentation increases audit risks and undermines claims.
e. Failure to Register on Time: Companies must register for corporation tax within three months of starting business activities.
f. CT600 Errors: Common mistakes include omitting supplementary pages or misreporting R&D claims.
g. Ignoring Associated Company Rules: Misunderstanding how thresholds are reduced by associated companies and period length can distort liabilities.
h. Not Updating HMRC: Failure to notify HMRC of changes (e.g. address, accounting period) causes compliance issues.
i. Over-Reliance on Software: Software errors or misconfigurations can lead to incorrect filings if not checked.

 

2. Compliance Tips

 

– Use reminders to track deadlines
– Keep accurate, up-to-date financial records
– Review HMRC guidance on allowable expenses
– Engage professional tax advisers
– Double-check supplementary pages on CT600
– Prepare for HMRC audits with organised records

 

Section H Summary: The most common corporation tax errors involve deadlines, poor records, and overlooked reliefs. Directors should treat corporation tax as a board-level responsibility, using robust controls and professional advice to minimise risks and optimise efficiency.

 

 

Section I: Role of Corporation Tax in Business Strategy

 

Corporation tax is not just a compliance obligation. It directly shapes how companies invest, structure their operations, manage profits, and plan growth. Finance directors and boards should integrate tax considerations into long-term strategy.

 

1. Investment Decisions

 

Tax reliefs strongly influence investment timing and type. For example:
– Capital allowances can encourage earlier purchases of machinery or vehicles.
– R&D relief incentivises technology and innovation spend.
Example: A manufacturer may advance equipment purchases to claim full AIA, reducing current year tax.

 

2. Business Structure and Location

 

Incorporation decisions often reflect tax efficiency, as corporate rates differ from income tax rates for sole traders or partnerships. Location is also strategic: some businesses choose UK regions with incentives or compare the UK’s 25% rate against lower international regimes.

 

3. Profit Retention and Distribution

 

Corporation tax affects whether profits are:
– Retained for reinvestment, or
– Distributed as dividends, triggering shareholder income tax.
Employee profit-sharing schemes and share options also have tax implications, influencing remuneration structures.

 

4. Mergers and Acquisitions

 

Corporation tax drives deal structuring. Considerations include:
– Capital allowances on acquired assets
– Restrictions on interest deductions
– Use of group relief and carried-forward losses
Example: An acquirer may value a target more highly if it has significant carried-forward losses available for offset.

 

5. Cash Flow Management

 

Tax payment schedules affect liquidity. Companies on quarterly instalments must forecast accurately. Directors often plan by accelerating expenses or deferring income, provided this aligns with accounting rules and HMRC compliance.

 

Section I Summary: Corporation tax influences investment, structuring, M&A, profit distribution, and cash flow. Treating tax as a strategic consideration ensures businesses remain compliant while protecting liquidity and maximising shareholder value.

 

 

Section J: Strategies for Effective Tax Planning and Management

 

Tax planning is about aligning compliance with efficiency and growth. Directors have legal duties to ensure tax obligations are met, making this a governance issue as much as a finance one. Strategic planning helps reduce liabilities while maintaining compliance.

 

1. Regular Tax Reviews and Audits

 

Internal audits and annual reviews identify relief opportunities and prevent errors. Reviews should focus on capital allowances, group relief, and correct application of R&D schemes.

 

2. Engage Professional Advisors

 

Advisors provide expertise on complex legislation, ensure claims are documented, and mitigate risks during HMRC enquiries.

 

3. Utilise Tax Reliefs and Incentives

 

Maximising reliefs reduces liabilities. Key opportunities include:
– R&D expenditure credit (20%)
– Capital allowances (AIA, WDA, FYA)
– Patent Box regime
– Creative industry credits (AVEC, VGEC)

 

4. Optimise Business Structure

 

Tax efficiency often depends on structure. Examples include incorporating partnerships, using subsidiaries for risk management, or reorganising to maximise group relief.

 

5. Strategic Timing of Expenditure and Income

 

Timing decisions can influence taxable profits. Accelerating expenditure to claim allowances earlier or deferring income recognition can smooth liabilities.

 

6. Implement Effective Record-Keeping

 

Records must be kept for at least six years. Accurate record-keeping underpins relief claims and reduces HMRC risk.

 

7. Monitor Legislative Changes

 

Corporation tax is subject to frequent reform. Current issues include R&D scheme changes, OECD Pillar 2 implementation, and possible future adjustments under Labour government policy.

 

8. Consider Tax in Strategic Decisions

 

Tax should inform decisions on acquisitions, capital projects, and dividend policy. Ignoring tax implications risks higher liabilities and reduced shareholder returns.

 

9. Use Tax-Efficient Investment Vehicles

 

Schemes such as EIS, SEIS, and VCTs help businesses raise capital by offering investors attractive tax breaks, improving funding options.

 

10. Plan for Tax Payments

 

Corporation tax should be built into cash flow forecasts, with reserves set aside throughout the year. This is critical for companies on quarterly instalments.

 

Section J Summary: Effective planning combines relief use, structural efficiency, accurate records, and awareness of legislative change. Directors who integrate tax into governance and strategy protect compliance, liquidity, and shareholder value.

 

 

Section K: Summary

 

Corporation tax is one of the most significant financial obligations for UK companies. With a main rate of 25% supported by a small profits rate and marginal relief, directors must ensure liabilities are correctly calculated, filed, and paid on time.

Key points include:
– UK companies are taxed on worldwide profits, and foreign companies on UK branches.
– The CT600 must be filed within 12 months of the accounting period end.
– Tax is due 9 months and 1 day after period end, or earlier for large/very large companies on instalments.
– Reliefs such as R&D, capital allowances, Patent Box, and creative sector credits can reduce liabilities.
– Common errors include late filing, poor records, and overlooked reliefs.
– Tax strategy influences investment, structuring, cash flow, and shareholder value.

Section K Summary: Corporation tax affects compliance, finance, and strategy. Strong processes help avoid HMRC penalties while supporting growth and resilience.

 

Section L: FAQs

 

What is the deadline for filing a corporation tax return?
The CT600 must be filed within 12 months of the accounting period end. For example, if the period ends on 31 March 2024, the deadline is 31 March 2025.

 

When must corporation tax be paid?
Most companies must pay within 9 months and 1 day of the period end. Large and very large companies may have to pay in quarterly instalments.

 

How do I register for corporation tax?
Companies must register with HMRC within three months of starting business activities. A UTR is issued by HMRC after incorporation.

 

What are the current corporation tax rates?
As of April 2023:
– 19% small profits rate up to £50,000 (adjusted)
– Marginal relief between £50,001 and £250,000
– 25% main rate above £250,000
Thresholds are reduced for associated companies and short accounting periods.

 

What records must be kept?
Companies must keep records of income, expenses, capital allowances, and supporting documentation for at least six years.

 

What penalties apply for late filing?
– £100 penalty if 1 day late
– Additional £100 if over 3 months late
– 10% of unpaid tax after 6 months
– A further 10% after 12 months

 

How does HMRC charge interest?
Interest accrues daily on late payments from the day after the due date until payment. The rate varies with the Bank of England base rate.

 

What reliefs are available?
Common reliefs include R&D, capital allowances, Patent Box, and creative sector credits. Group relief also allows offsetting of losses within a group.

 

Are EIS and SEIS corporation tax reliefs?
No. They are investor reliefs providing income tax and capital gains tax incentives, but they help companies attract equity funding.

 

How can directors ensure compliance?
Set reminders, maintain accurate records, seek professional advice, review returns, and embed tax compliance at board level.

 

Section L Summary: Corporation tax FAQs address the key compliance issues directors face: deadlines, rates, records, penalties, and reliefs. The answers underline the importance of planning, professional advice, and board-level oversight.

 

 

Section M: Glossary

 

Accounting Period: The period covered by a company’s accounts, usually 12 months, used for corporation tax assessment.

Annual Investment Allowance (AIA): 100% relief on qualifying capital expenditure up to £1 million per year.

Associated Companies: Companies under common control. The number of associated companies reduces thresholds for small profits rate, marginal relief, and instalment payments.

Capital Allowances: Relief for capital expenditure, replacing depreciation in tax calculations.

Corporation Tax: A tax on taxable profits of UK-resident companies and UK branches of foreign companies.

CT600: The corporation tax return form submitted to HMRC.

First-Year Allowance (FYA): 100% relief for certain qualifying expenditure such as zero-emission vehicles.

Group Relief: Allows losses of one group company to be offset against another’s profits.

HM Revenue & Customs (HMRC): The UK authority responsible for tax collection and compliance.

Loss Carry-Back/Carry-Forward: Rules allowing trading losses to be set against earlier or later profits.

Marginal Relief: Relief tapering corporation tax between the small profits rate and the main 25% rate.

Marginal Relief Fraction: Formula for calculating marginal relief: (3/200) × (Upper Limit – Augmented Profits) × (Taxable Profits ÷ Standard Rate Profits).

OECD Pillar 2: International framework introducing a 15% minimum effective corporate tax rate.

Patent Box: Regime taxing qualifying patent-derived profits at 10%.

Profits: Surplus after allowable expenses, forming the basis for corporation tax.

Qualifying Expenditure: Costs eligible for relief such as R&D or capital assets.

R&D Tax Relief: Relief for innovation expenditure; from April 2024 most claims fall under the merged RDEC scheme.

Small Profits Rate: 19% corporation tax rate applying to profits up to £50,000 (adjusted).

Super Deduction: Temporary 130% capital allowance available between April 2021 and March 2023 (now expired).

Taxable Profits: Profits chargeable to corporation tax after reliefs and adjustments.

Unique Taxpayer Reference (UTR): A 10-digit number issued by HMRC to identify a company for tax purposes.

Writing Down Allowance (WDA): Capital allowance enabling relief spread over several years.

 

Section N: Additional Resources

 

HMRC Corporation Tax Guide
https://www.gov.uk/corporation-tax

Registering for Corporation Tax
https://www.gov.uk/register-for-corporation-tax

File Your Company Tax Return (CT600)
https://www.gov.uk/file-your-company-tax-return

Corporation Tax Rates and Reliefs
https://www.gov.uk/corporation-tax-rates

Research and Development Reliefs
https://www.gov.uk/guidance/corporation-tax-research-and-development-rd-relief

Capital Allowances
https://www.gov.uk/capital-allowances

Patent Box
https://www.gov.uk/guidance/corporation-tax-the-patent-box

Creative Industry Tax Reliefs / Expenditure Credits
https://www.gov.uk/guidance/corporation-tax-creative-industry-tax-reliefs

Group Relief Guidance
https://www.gov.uk/hmrc-internal-manuals/corporate-finance-manual/cfm90700

OECD Pillar 2 – Global Minimum Tax
https://www.oecd.org/tax/beps/pillar-two/

 

Final Summary: The glossary clarifies technical terms, while the resources provide authoritative HMRC and OECD guidance. Together with the main sections, this gives directors and finance leaders a complete, legally accurate guide to corporation tax in the UK.

 

Author

Gill Laing is a qualified Legal Researcher & Analyst with niche specialisms in Law, Tax, Human Resources, Immigration & Employment Law.

Gill is a Multiple Business Owner and the Managing Director of Prof Services Limited - a Marketing & Content Agency for the Professional Services Sector.

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Legal Disclaimer

The matters contained in this article are intended to be for general information purposes only. This article does not constitute legal or financial advice, nor is it a complete or authoritative statement of the law or tax rules and should not be treated as such. Whilst every effort is made to ensure that the information is correct, no warranty, express or implied, is given as to its accuracy and no liability is accepted for any error or omission. Before acting on any of the information contained herein, expert professional advice should be sought.

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