UK corporation tax for Financial Year 2026 (the period from 1 April 2026 to 31 March 2027) keeps the two-rate structure that has been in place since April 2023. The headline rates are unchanged, but the marginal relief band between £50,000 and £250,000 still trips up company directors — and the associated-company rules can quietly pull your thresholds down.
The Rates for FY2026
| Band | Taxable profits | Rate |
|---|---|---|
| Small profits rate | Up to £50,000 | 19% |
| Marginal relief band | £50,001 – £250,000 | Effective 26.5% |
| Main rate | Over £250,000 | 25% |
Note that “Financial Year 2026” for corporation tax runs 1 April 2026 to 31 March 2027 — different from the 6 April – 5 April personal tax year. If your accounting period straddles 1 April, profits are time-apportioned between financial years, though in practice the rates have been identical across recent years.
How Marginal Relief Works
If your profits land between £50,000 and £250,000, you don’t simply pay 25% on everything. You calculate tax at the main rate of 25% and then subtract marginal relief:
Marginal relief = (Upper limit − Profits) × (Augmented profits ÷ Profits) × 3/200
For a standalone company with no other income, this simplifies to:
Marginal relief = (£250,000 − Profits) × 3/200
The 3/200 fraction (0.015) is set in legislation. The result is an effective marginal rate of 26.5% on every pound of profit in the band — higher than the 25% main rate, because each extra pound gradually claws back the benefit of the 19% rate on the first £50,000.
Worked Example
Maple Joinery Ltd has taxable profits of £90,000 for the year ending 31 March 2027.
Step 1 — tax at the main rate: £90,000 × 25% = £22,500
Step 2 — marginal relief: (£250,000 − £90,000) × 3/200 = £160,000 × 0.015 = £2,400
Step 3 — corporation tax payable: £22,500 − £2,400 = £20,100
Effective rate: £20,100 ÷ £90,000 = 22.3%
Tax at Different Profit Levels (FY2026)
| Taxable profits | Calculation | Tax payable | Effective rate |
|---|---|---|---|
| £40,000 | £40,000 × 19% | £7,600 | 19.0% |
| £50,000 | £50,000 × 19% | £9,500 | 19.0% |
| £90,000 | £22,500 − £2,400 | £20,100 | 22.3% |
| £150,000 | £37,500 − £1,500 | £36,000 | 24.0% |
| £200,000 | £50,000 − £750 | £49,250 | 24.6% |
| £250,000 | £250,000 × 25% | £62,500 | 25.0% |
Associated Companies
The £50,000 and £250,000 limits are divided by the number of associated companies plus one. This stops business owners from splitting profits across several companies to keep each one in the 19% band.
| Associated companies | Lower limit (each) | Upper limit (each) |
|---|---|---|
| None (standalone) | £50,000 | £250,000 |
| 1 | £25,000 | £125,000 |
| 2 | £16,667 | £83,333 |
| 3 | £12,500 | £62,500 |
So if your company has one associated company, the small profits rate only applies up to £25,000, and the 25% main rate begins at £125,000 of profit.
What counts as “associated”
Two companies are associated if one controls the other, or both are under the control of the same person or group (broadly, more than 50% of share capital, voting power, or rights to income and assets). Control held by associates (close family, business partners) can be attributed where there is “substantial commercial interdependence” between the companies. Dormant companies — no trade, no income, no assets — are excluded from the count.
Payment and Filing Deadlines
For companies that are not large (profits under £1.5 million), the deadlines are:
| Obligation | Deadline |
|---|---|
| Pay Corporation Tax | 9 months and 1 day after the accounting period ends |
| File the Company Tax Return (CT600) | 12 months after the accounting period ends |
For a 31 March 2027 year-end: pay by 1 January 2028, file by 31 March 2028.
Large companies (augmented profits over £1.5 million, reduced by associated companies) must pay in quarterly instalments, with the first instalment due in month 7 of the accounting period — well before the return is even filed.
Reducing the Bill
Corporation tax is charged on taxable profits, so the legitimate levers are below the line:
- Capital allowances — full expensing gives 100% first-year relief on qualifying plant and machinery
- Pension contributions — employer contributions are deductible
- Salary vs dividends — director remuneration is a deductible cost; dividends are not (they’re paid from post-tax profit). See our take-home pay calculator to model extraction
- R&D relief — if you carry out qualifying research and development
Key Takeaway
For FY2026 (1 April 2026 – 31 March 2027), corporation tax is 19% up to £50,000, 25% above £250,000, and an effective 26.5% in the marginal relief band using the 3/200 fraction. Watch the associated-company rules — each associate divides your thresholds and can push you into the higher effective rate sooner than expected.
Use the corporation tax calculator to see your exact bill, and the VAT calculator if your turnover is approaching the £90,000 registration threshold.