Written by Natalie Sweeney, FMAAT
Fellow of the Association of Accounting Technicians · 20+ years experience · Rocket Accountants, Benfleet, Essex
Corporation Tax is the single largest tax bill for most UK limited companies. With rates now at 25% for larger profits, getting your Corporation Tax calculation right — and claiming every legitimate deduction — can save your Essex business thousands of pounds every year. At Rocket Accountants, we prepare Corporation Tax returns for limited companies across Benfleet, Basildon, Southend, Chelmsford, Colchester and all of Essex, ensuring compliance and maximising tax efficiency.
Corporation Tax Rates for 2025/26
The UK Corporation Tax system operates on a tiered rate structure. From April 2023, the main rate increased to 25%, but small companies with profits up to £50,000 still benefit from the small profits rate of 19%. Between £50,000 and £250,000, marginal relief applies to gradually bridge the gap.
Profits up to £50,000 — 19%
Small profits rate — applies to most micro and small businesses
Profits £50,001 — £250,000 — Marginal relief
Effective rate gradually increases from 19% to 25%
Profits above £250,000 — 25%
Main rate — applies to all profits for large companies
Important: The thresholds are reduced if you have associated companies (companies under common control). For example, if you control two companies, the £50,000 threshold is split to £25,000 each. This is a common trap for business owners with multiple ventures. We review your group structure to ensure you are not paying more tax than necessary.
The marginal relief calculation is not straightforward. The formula is: 3/200 × (£250,000 − profit). For a company with £100,000 profit, the effective rate is approximately 22.75%. We calculate this precisely for every client to ensure the correct amount is paid.
What Counts as Taxable Profit?
Your Corporation Tax liability is based on your taxable total profits, which is not the same as your accounting profit. Several adjustments are made:
- Accounting profit per your financial statements is the starting point
- Add back: depreciation and any disallowed expenses (e.g., entertainment, fines, penalties)
- Add back: certain director's loan interest if not charged at HMRC-approved rates
- Deduct: capital allowances (annual investment allowance, writing down allowances, first-year allowances)
- Deduct: research and development (R&D) tax relief enhancement
- Deduct: certain losses brought forward from previous accounting periods
This is why you cannot simply look at your profit and loss account and apply the tax rate. The tax computation requires careful analysis of every item, and missing a legitimate deduction is the same as overpaying tax.
Capital Allowances: The Biggest Tax Saver for Small Companies
Capital allowances let you deduct the cost of business equipment, vehicles, and fixtures from your taxable profits. For small companies, these are often the most significant tax-saving opportunity:
Annual Investment Allowance (AIA)
100% deduction on qualifying plant and machinery up to £1 million per year. This covers most business equipment, computers, machinery, tools, and office furniture. Vehicles are excluded except for commercial vans and certain low-emission cars.
Full Expensing (100% First-Year Allowance)
Introduced from April 2023, this gives unlimited 100% first-year relief on qualifying plant and machinery. It effectively replaces the super-deduction and has no annual limit. This is a major incentive for companies investing in growth.
50% First-Year Allowance
For qualifying special-rate assets (typically long-life assets, integral features, and certain buildings fixtures), you can claim 50% in the first year and the rest under writing down allowances.
Writing Down Allowances (WDA)
18% per year on the main pool, 6% per year on the special rate pool. Applied to assets that do not qualify for AIA or full expensing, or to the balance after AIA has been used.
Electric Vehicle Allowance
New zero-emission cars attract 100% first-year allowance if purchased new and unused. Company electric vehicles are also highly tax-efficient for the director receiving the benefit, with low benefit-in-kind rates.
Timing matters: Capital allowances are based on your accounting period. If you buy a £50,000 machine in March and your year end is 31 March, you get the full deduction in that year. If your year end is 1 April, you may need to apportion. We plan capital expenditure with your year end in mind to maximise the tax relief.
R&D Tax Relief: The Hidden Gem for Essex Businesses
Research and Development (R&D) tax relief is not just for tech companies or pharmaceutical giants. Any limited company that overcomes scientific or technological uncertainty through innovation may qualify. We have helped construction firms, manufacturers, software developers, food producers, and even beauty product companies in Essex claim R&D relief.
For SMEs, the R&D expenditure credit works as follows:
- You identify qualifying R&D costs: staff costs, subcontractors, materials, utilities, and software used directly in the R&D project
- For the SME scheme (now merged under the single R&D scheme from April 2024), you can claim an enhanced deduction of 86% of qualifying spend
- Loss-making companies can surrender the loss for a cash payment at 10% of the enhanced expenditure (approx. 8.6% of actual spend)
- Profitable companies reduce their taxable profit by 186% of the qualifying spend, saving tax at 19% or 25% depending on profit level
A typical Essex manufacturing company spending £40,000 on R&D could save £7,600 in Corporation Tax or receive a £3,440 cash payment if loss-making. The key is recognising that R&D does not mean lab coats — it means solving technical problems that are not readily solvable by a competent professional in your field.
Director\'s Salary vs Dividends: The Optimal Mix in 2025/26
One of the most common questions we get from Essex company directors is: "How should I pay myself?" The answer depends on your personal circumstances, but the general principle is:
1. Take a small salary
Set at the National Insurance threshold (£12,570 for 2025/26) to qualify for state pension credits without triggering employee's NI. This is fully deductible for Corporation Tax.
2. Take the rest as dividends
Dividends are taxed at lower rates (8.75% basic, 33.75% higher, 39.35% additional) and are not subject to National Insurance. The dividend allowance is £500 for 2025/26.
3. Consider pension contributions
Employer pension contributions are Corporation Tax deductible and carry no personal tax or NI for the director. This is often the most tax-efficient extraction for profits you do not need immediately.
4. Beware of the £100,000 taper
Personal allowances reduce by £1 for every £2 of income above £100,000. If your total income is near this threshold, a small shift from salary to dividends or pension can save thousands.
For a company with £80,000 profit, the optimal mix typically saves around £6,000–£8,000 compared to taking everything as salary. We calculate this precisely for each director based on their total income, spouse\'s income, and other tax factors.
Corporation Tax Deadlines and Payment Rules
Corporation Tax operates on a self-assessment basis. Unlike personal tax, there is no fixed January deadline — your deadline depends on your accounting period:
- Your Corporation Tax return (CT600) is due 12 months after the end of your accounting period
- The tax payment is due 9 months and 1 day after the end of your accounting period
- For companies with profits over £1.5 million, quarterly instalment payments are required
- Penalties for late filing: £100 at 1 day, £500 at 3 months, 10% of tax at 6 months, 20% at 12 months
- Interest on late payment: HMRC charges daily interest on overdue Corporation Tax, currently at 7.75%
Many small companies in Essex miss the filing deadline because they assume it aligns with their VAT or Self Assessment dates. We send automated reminders to all clients 60 days, 30 days, and 7 days before each deadline.
Common Corporation Tax Mistakes to Avoid
Not claiming all available capital allowances
Many companies simply depreciate assets over their accounting life and miss the opportunity to claim 100% AIA or full expensing. This is the most expensive mistake we correct.
Misclassifying director's loan account transactions
If you borrow money from your company, HMRC charges a 33.75% tax charge on the outstanding balance if not repaid within 9 months of the year end. We monitor director's loan accounts continuously to avoid this.
Ignoring the associated company rules
If you run two companies, the small profits rate threshold splits. Many business owners accidentally pay 25% on profits that should have been at 19% because they did not plan the group structure.
Failing to claim R&D because you think you are not "technical"
R&D relief is available for any company solving technical problems. We have helped builders, caterers, and cleaning companies claim significant relief — the key is the uncertainty, not the industry.
Not reviewing the optimal salary-dividend split annually
Tax thresholds change every year. The optimal mix for 2024/25 may not be optimal for 2025/26. We review this for every director-client every spring.
Get Your Corporation Tax Right
Our Essex accountants prepare Corporation Tax returns for limited companies across every industry. From capital allowances and R&D claims to director\'s remuneration planning, we make sure you pay exactly what you owe — and not a penny more.
Frequently Asked Questions
How much does it cost to prepare a Corporation Tax return?
At Rocket Accountants, Corporation Tax preparation is included in our monthly accounting packages. Bronze (£50/month) covers straightforward returns. Silver (£75/month) adds tax planning and quarterly reviews. Gold (£125/month) includes R&D claims, group structures, and strategic planning. We do not charge surprise extra fees at year end.
Can I prepare my own Corporation Tax return?
Technically yes, using HMRC's online CT600 service. However, the complexity of capital allowances, R&D claims, associated company rules, and marginal relief means most DIY returns either overpay tax or contain errors that trigger HMRC enquiries. The cost of professional preparation is typically recovered many times over in tax savings.
What records do I need to keep for Corporation Tax?
You must keep all accounting records, bank statements, invoices, receipts, and payroll records for at least 6 years from the end of the accounting period. We store all client records digitally in Xero, so you never need to worry about losing paperwork.
Do I pay Corporation Tax on my director's salary?
No. Your director's salary is a deductible expense for the company, so it reduces your Corporation Tax bill. However, you pay Income Tax and National Insurance on the salary personally. This is why the salary-dividend mix is so important — we optimise the total tax paid by both you and your company.
About the Author
Natalie Sweeney FMAAT is the founder and director of Rocket Accountants, based at 105 London Road, Benfleet, Essex. Natalie is a Fellow Member of the Association of Accounting Technicians (FMAAT) with over 20 years of experience in bookkeeping, payroll, accounting and tax. Formerly part of MSB Benfleet, Rocket Accountants has grown to serve sole traders, limited companies and individuals across all 44+ Essex towns.