Corporation Tax

Introduction to Corporation Tax

Corporation Tax is one of the most important taxes your business will ever deal with. If you run a limited company in the UK, Corporation Tax applies to the profits your business makes and must be calculated, reported, and paid correctly every year.

Unlike Income Tax, which applies to individuals and sole traders, Corporation Tax applies to UK-registered limited companies and some organisations, including clubs and associations. Understanding how it works — and how to minimise it legally — can have a major impact on your company’s cash flow, growth, and long-term success.

At its core, Corporation Tax is charged on:

Trading profits
Investment income
Capital gains (after allowances and reliefs)

This page explains what Corporation Tax is, how much you pay, key deadlines, allowable deductions, and how professional tax planning can reduce your bill.

Who Pays Corporation Tax?

You must register for and pay Corporation Tax if your business operates as a limited company in the UK. This applies whether you are actively trading or dormant.

Corporation Tax typically applies to:

Private limited companies (Ltd)
Public limited companies (PLC)
UK branches of overseas companies
Members’ clubs and associations (in some cases)

You do not pay Corporation Tax if you are:

A sole trader
In a general partnership (partners pay Income Tax instead)
A limited liability partnership (LLP), unless structured otherwise

Even if your company makes no profit, you may still need to file a Corporation Tax return to confirm this to HM Revenue & Customs.

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Corporation Tax Rates in the UK

Corporation Tax is charged at different rates depending on your company’s taxable profits.

Current UK Corporation Tax structure:

Small Profits Rate: Applies to companies with profits below a set threshold
Main Rate: Applies to companies with higher profits
Marginal Relief: Applies if profits fall between the two thresholds

Because rates and thresholds can change, it’s essential to plan ahead — particularly if your company’s profits fluctuate year to year.

Poor forecasting can result in:

Unexpected tax bills
Missed reliefs
Cash flow pressure

A qualified accountant can ensure your business applies the correct rate and takes advantage of available reliefs.

What Profits Are Subject to Corporation Tax

Corporation Tax is not charged on turnover — it is charged on taxable profit.

Taxable profit generally includes:

Sales income minus allowable expenses
Investment income (e.g. interest)
Capital gains on the sale of assets

Before tax is calculated, your accountant will:

Prepare statutory accounts
Adjust profits for tax purposes
Apply reliefs and allowances

This process ensures your tax bill is accurate and compliant, while avoiding overpayment.

Allowable Expenses and Deductions

One of the most effective ways to reduce Corporation Tax is by claiming all legitimate business expenses.

Common allowable expenses include:

Staff wages and employer NICs
Office rent and utilities
Professional fees (accountants, solicitors)
Marketing and advertising
Software and subscriptions
Travel costs (business use only)

Expenses must be:

Wholly and exclusively for business purposes
Properly documented

Incorrect or missed claims can significantly increase your tax bill, which is why structured bookkeeping and expert review are essential.

Capital Allowances and Asset Purchases

Rather than deducting large purchases in one go, businesses often claim capital allowances.

These apply to:

Equipment and machinery
Computers and IT systems
Vehicles (with restrictions)
Certain building improvements

The Annual Investment Allowance (AIA) may allow you to deduct the full cost of qualifying assets in the year of purchase, reducing your Corporation Tax liability immediately.

Strategic timing of asset purchases can:

Lower taxable profits
Improve cash flow
Support business growth

This is an area where proactive tax planning delivers real financial benefits.

Corporation Tax Returns and Deadlines

Every limited company must file a Corporation Tax return (CT600).

Key deadlines:

Register for Corporation Tax: Within 3 months of starting trading
Pay Corporation Tax: Usually within 9 months and 1 day after year-end
File CT600: Within 12 months of the accounting period end

Late filing or payment can result in:

Automatic penalties
Interest charges
HMRC compliance checks

Using an accountant ensures deadlines are met and returns are filed accurately the first time.

Tax Planning and Reducing Corporation Tax

Corporation Tax planning is about legally minimising tax, not avoiding it.

Effective strategies may include:

Director salary and dividend optimisation
Pension contributions
Timing income and expenses
Group relief (for multiple companies)
Loss relief and carry-forward planning

Good tax planning is proactive — not something done after the year has ended. The earlier it starts, the more control you have over your final tax position.

Common Corporation Tax Mistakes to Avoid

Many SMEs overpay Corporation Tax due to avoidable errors.

Common mistakes include:

Missing allowable expenses
Incorrect asset treatment
Late filing penalties
Poor record-keeping
No forward tax planning

These issues often arise when businesses rely solely on software or handle tax internally without expert oversight.

Professional support reduces risk and often pays for itself through tax savings.

How an Accountant Can Help with Corporation Tax

Corporation Tax is not just a compliance requirement — it’s a planning opportunity.

A specialist accountant will:

Calculate and file your Corporation Tax return
Ensure compliance with HMRC regulations
Identify tax-saving opportunities
Advise on growth-focused tax strategies
Act as your representative with HMRC

Whether you’re a startup or an established company, expert guidance gives you confidence, clarity, and control over your business finances.