Corporation Tax
& CT600 Returns
Corporation Tax is charged on the taxable profits of UK limited companies. A company must file its Company Tax Return (CT600) within 12 months of the end of its accounting period, and usually pays the tax 9 months and one day after the period ends. We prepare and file CT600 returns, apply the reliefs and allowances available, and keep both deadlines in view.
Who this is for
- UK limited companies, including loss-making companies, which must still file a return when HMRC asks for one
- Newly incorporated companies filing their first Company Tax Return
- Companies with profits between £50,000 and £250,000, where Marginal Relief applies
- Companies with associated companies, whose profit thresholds are reduced
How we help
- Work out taxable profit from your statutory accounts, which is not the same as the accounting profit
- Prepare and file the CT600 return online with HMRC
- Identify the allowances and reliefs available, including capital allowances on qualifying spending
- Confirm the tax payable and the payment deadline, so the bill does not arrive as a surprise
What’s included
- Corporation Tax computation
- CT600 return prepared and filed online
- Capital allowances claims on qualifying spending
- Marginal Relief calculations where profits fall between the two thresholds
Key dates and figures
Checked against GOV.UK on 24 September 2026. Rates and thresholds change, so confirm how they apply to your own circumstances before acting on them.
- Main rate
25% where profits are more than £250,000
Source: Corporation Tax rates, expenses and reliefs- Small profits rate
19% where profits are £50,000 or less
Source: Corporation Tax rates, expenses and reliefs- Marginal Relief
May apply to profits between £50,000 and £250,000; both thresholds are reduced for short periods and associated companies
Source: Corporation Tax rates, expenses and reliefs- Payment deadline
9 months and 1 day after the end of the accounting period (taxable profits up to £1.5 million)
Source: Pay Corporation Tax- Profits over £1.5 million
Corporation Tax is paid in instalments
Source: Pay Corporation Tax- Filing deadline
12 months after the end of the accounting period
Source: Company Tax Returns- Late filing penalty
£200 one day late, another £200 at 3 months; £1,000 each if late 3 times in a row
Source: Company Tax Returns: penalties for late filing
A Family Business Brought Back Into Compliance
An established family business whose accounting and taxation affairs had become difficult after several years of inadequate record keeping and inconsistent professional advice — records reconstructed, historic Corporation Tax and VAT positions reviewed, and controls put in place.
Corporation Tax (CT600): Frequently Asked Questions
Plain answers to the questions we are asked most often.
Companies with profits over £250,000 pay the main rate of 25%. Companies with profits of £50,000 or less pay the small profits rate of 19%. Between the two, Marginal Relief may reduce the effective rate.
Both thresholds are reduced proportionately for accounting periods shorter than 12 months and by the number of associated companies, so a group of related companies can reach the main rate at lower profit levels.
For companies with taxable profits up to £1.5 million, Corporation Tax is due 9 months and one day after the end of the accounting period. Companies with profits above £1.5 million pay in instalments.
The Company Tax Return itself is due 12 months after the end of the period, so the tax is normally payable before the return is filed. HMRC charges interest on late payments.
Yes. If HMRC has sent a notice to deliver a Company Tax Return, you must file one even if the company made a loss or has no Corporation Tax to pay. Filing also records the loss, which may be available to set against profits in other periods.
The penalty is £200 if the return is one day late and another £200 at three months. At six months, HMRC estimates the Corporation Tax bill and adds a penalty of 10% of the unpaid tax, with a further 10% at twelve months. If a return is late three times in a row, the £200 penalties rise to £1,000 each.
Revenue expenses incurred wholly for the business, the day-to-day running costs, can generally be deducted when working out taxable profit. Some costs are specifically disallowed, such as entertaining clients.
Capital expenses, such as buying a van or equipment used for several years, cannot be deducted directly, but the company may be able to claim capital allowances on them instead.
Related services
Annual Accounts
Statutory year-end accounts and financial statements for companies, partnerships, and sole traders, prepared for filing at Companies House and HMRC.
VAT & Making Tax Digital
VAT registration, quarterly returns, and full Making Tax Digital compliance for your business.
Payroll & Bookkeeping
PAYE and Real Time Information payroll, workplace pension administration, and ongoing bookkeeping with management accounts.
Related insights
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Tell us about your business or your personal tax affairs, and we will explain how we can help.
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