The current main rate of corporation tax is 19% for the 2022/23 tax year. This has been the rate since April 1, 2017. Prior to 2017, the main rate was 20% from April 1, 2015. Before that it was 21% from April 1, 2014 and 23% from April 1, 2013. The main rate is set to increase to 25% from April 1, 2023 for companies with profits over £250,000. For companies with profits below £50,000 the rate is 19%. There is a marginal sliding scale for profits between £50,000 and £250,000.

The main rate was as high as 52% in the early 1970s. It was gradually reduced over time to reach 28% by 2008. Additional rates have existed at times for ring-fenced profits like oil and gas extraction and for the banking sector. The current 19% rate is the lowest main rate since the 1970s. The 2023 increase to 25% for bigger profits will be the first rise in the main rate since 2015. So in summary, the corporation tax main rate has steadily declined from over 50% in the 1970s to 19% today, with a planned increase to 25% for larger profits coming in 2023. The trend has been downwards but is set to rise for the first time in many years.

To calculate your small business Corporation Tax, you would need some knowledge in accounting, along with correct bookkeeping. You will also need to

• Understand taxable profit vs accounting profit – Know the differences between profit calculated for accounting purposes and profit calculated for tax purposes. Tax deductions and rules differ.
• Learn tax adjustments – You’ll need to know how to make tax adjustments to accounting profit, including additions and deductions. Common examples are depreciation, interest, capital allowances, losses, etc.
• Learn how to treat capital gains and losses – Know how capital disposals of assets are treated and taxed.
• Understand group relief and losses – Rules around using current year losses and carrying forward previous losses.
• Learn double taxation relief – How to claim relief for tax paid overseas to avoid double taxation.
• Know tax reliefs and incentives – Such as R&D tax credits that can reduce taxable profit.
• Understand marginal relief – The rules around gradual increase in tax rates for profit bands.

It’s always best to seek expert assistance from a business accountant to check your corporation tax return.

HMRC provides several methods to pay Corporation Tax, and it is worth bearing in mind the due date of when you must pay. If you miss out on a deadline, you will be liable for interest payments. However, if you choose to pay your Corporation Tax ahead of time, HMRC will pay interest to your company.

If you have calculated your company tax and do not owe Corporation Tax, you must tell HMRC that you have no tax to pay – you must not suppose that you need not inform HMRC because you do not have anything to pay.

Corporation tax is normally paid in quarterly installments for companies with profits over £1.5 million. Deadlines are 6, 9, 12 and 15 months after the start of the accounting period.

However, installment payments are not required for small companies in their first accounting period if it is less than 12 months. Tax is paid in full 9 months and 1 day after the end of that period.

Installments are also not required if the total tax liability for the period is less than £10,000 (or less than £10,000 annualized if period is under 12 months). Or if profits are £10 million or less and the company didn’t exist in the prior 12 months or had profits under £1.5 million or tax under £10,000. In these cases, tax can be paid in full by the normal due date.

If final liability is lower than installments paid, the company receives a refund after filing the return. If liability is higher, a balancing payment is due 9 months and 1 day after the period end.

Even if no tax is due, the company must file the return by 12 months after the period end and notify HMRC of the nil payment.

There are a number of factors that influence  fees our company tax accountants charge companies for calculating taxes and tax compliance work:

• Company size – Fees are typically higher for larger companies as they require more time and staff to handle larger volumes of transactions and greater complexity.
• Multinational activities – Companies with international operations and subsidiaries require extra time to handle cross-border tax obligations.
• Company structure – More complex group structures, multiple entities, dividends and tax planning add layers of work.
• Nature of revenue and expenses – More complex revenue streams and expenses require additional review and documentation.
• Claims and reliefs – The level of tax reliefs claimed like R&D credits impacts fees.
• Tax advice needs – Extensive tax planning and advisory work commands higher fees.
• Filing requirements – More tax filings and increased disclosure requirements create more prep work.
• Accounting system – Simple accounting software or records vs sophisticated ERP systems impacts workload.
• Industry – Specialist knowledge needed for certain industries like oil & gas, finance.

So in essence, the key factors are the size and complexity of the company’s tax affairs, its business structure, the extent of tax advice needed, and the level of tax compliance obligations. The greater the scope, the higher the likely fees.

Corporation tax can be reduced by utilising reliefs available to business. 

• Claim all eligible tax reliefs – Like R&D tax credits, capital allowances, loss reliefs, etc. Follow rules to maximize claims.
• Make tax-deductible payments – Pension contributions for employees, interest payments, some employee benefits.
• Review timing of income and expenditures – Delaying income recognition or accelerating expenditures prior to year-end may help reduce taxable profit.
• Consider optimal business structure.
• Locate operations in lower tax jurisdictions.
• Set up separate overseas trading entities – Profits from overseas operations not taxed in UK until repatriated. Use transfer pricing cautiously between entities.
• Use tax incentives for investment – Like R&D tax credits, Enterprise Zones, Creative Industry tax reliefs.
• Claim capital allowances for equipment – Accelerate tax relief on capital expenditures.
• Take advantage of tax treaties – Different tax rules may apply under certain international treaties.

The key is maximizing permitted tax reliefs, allowances, deductions, timing of items, and structuring in a tax-efficient manner. Professional advice is recommended given tax rules complexity.

You can revise your tax returns if there is a major difference between disclosed and actual liability. In case of small differences and if there is no loo to revenue, adjustments can be made in the current year and explained in notes to the accounts. For other amendments 

• For small underpayments of corporation tax, an amendment can be made within 9 months and 1 day after the end of the accounting period.
• For larger errors, or errors spotted later, an amendment can be made within 4 years after the end of the accounting period.
• For overpaid tax, an amendment can be made within 4 years of the end of the accounting period to claim a repayment.
• For losses, you have 4 years to amend and claim tax relief by carrying back losses against previous year profits.
• For claims such as R&D tax credits, the time limit is 2 years after the end of the accounting period.
• Amendments are made by filing a “Company Tax Return Amendment Request” with HMRC detailing the changes.
• Interest and penalties may apply if additional tax is due or mistakes were careless.