UK Corporation Tax Marginal Relief Calculator
Build a clear corporation tax marginal relief calculation example with adjusted limits for associated companies and short accounting periods.
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UK Corporation Tax Marginal Relief Calculation Example: Expert Guide
Marginal relief is one of the most important UK corporation tax concepts for owner-managed companies and growing businesses. It sits between the small profits rate and the main rate, and it can materially change your effective tax rate as profits rise through the middle band. If you are looking for a practical, reliable uk corporation tax marginal relief calculation example, this guide breaks down the framework, the formula, the adjustments, and the planning implications in plain English.
1) Why marginal relief exists and who it affects
From 1 April 2023, the UK moved from a single corporation tax rate to a tiered structure for most companies:
- Small profits rate: 19% for companies with profits at or below the lower limit.
- Main rate: 25% for companies with profits at or above the upper limit.
- Marginal relief band: Companies between the two limits get relief that tapers from the main rate back toward the small profits rate.
In practice, marginal relief prevents a sudden jump from 19% to 25%. Instead, it creates a gradual transition. That means your effective rate can be somewhere between 19% and 25%, depending on your taxable total profits and augmented profits.
2) Current UK structure at a glance
| Financial Year | Small Profits Rate | Main Rate | Lower Limit | Upper Limit | Marginal Relief Fraction |
|---|---|---|---|---|---|
| FY 2023-24 | 19% | 25% | £50,000 | £250,000 | 3/200 |
| FY 2024-25 | 19% | 25% | £50,000 | £250,000 | 3/200 |
| FY 2025-26 | 19% | 25% | £50,000 | £250,000 | 3/200 |
Limits are reduced for short accounting periods and divided by the number of associated companies.
3) Core formula for marginal relief
The standard form often used in guidance is:
Marginal Relief = (Upper Limit – Augmented Profits) × (Taxable Total Profits / Augmented Profits) × Fraction
Then:
Corporation Tax = (Taxable Total Profits × Main Rate) – Marginal Relief
Key terms:
- Taxable Total Profits (TTP): profit chargeable to corporation tax after adjustments.
- Augmented Profits (A): broadly TTP plus exempt distributions from companies not in the same group.
- Fraction (F): currently 3/200.
- Upper and lower limits: subject to pro-rating for short periods and division by associated companies.
If your augmented profits are below the adjusted lower limit, you usually pay at 19%. If they are above the adjusted upper limit, you pay 25%. In between, marginal relief applies.
4) Worked uk corporation tax marginal relief calculation example
Assume the following facts for a 12-month period:
- Taxable total profits: £120,000
- Exempt distributions: £5,000
- Associated companies: 1 (just itself)
- Financial year settings: 19% small rate, 25% main rate, fraction 3/200
Step 1: Calculate augmented profits.
Augmented profits = £120,000 + £5,000 = £125,000
Step 2: Compare with limits. For a full year and one company, limits stay at £50,000 and £250,000. Since £125,000 is between limits, marginal relief applies.
Step 3: Compute marginal relief.
MR = (250,000 – 125,000) × (120,000 / 125,000) × (3/200)
MR = 125,000 × 0.96 × 0.015 = £1,800
Step 4: Compute main-rate tax before relief.
Main-rate tax = £120,000 × 25% = £30,000
Step 5: Deduct marginal relief.
Corporation tax due = £30,000 – £1,800 = £28,200
Effective tax rate in this example is £28,200 / £120,000 = 23.5%, which sits between 19% and 25%.
5) Why associated companies matter so much
Many businesses get caught here. The lower and upper limits are divided by the number of associated companies. If you have two associated companies in total, your limits are halved. If you have five, they are divided by five. This can push you into marginal relief or the main rate much earlier than expected.
Example: with 2 associated companies for a full year, limits become:
- Lower limit: £50,000 / 2 = £25,000
- Upper limit: £250,000 / 2 = £125,000
A company earning profits around £120,000 may be close to the upper limit in that case, even though it looks mid-range under standalone limits.
6) Short accounting periods and limit pro-rating
If your accounting period is shorter than 12 months, you also scale limits by time. For a 6-month period, full-year limits are halved before any associated company split is applied.
Illustration for 6 months with one company:
- Lower limit: £50,000 × 6/12 = £25,000
- Upper limit: £250,000 × 6/12 = £125,000
This means short periods can produce main-rate outcomes even when annualized profits feel moderate. In planning, always evaluate timing, period-end dates, and one-off transactions.
7) Comparison table: tax outcomes by scenario
| Scenario | TTP (£) | Augmented Profits (£) | Band | Estimated CT (£) | Effective Rate |
|---|---|---|---|---|---|
| A: Small company, no distributions | 40,000 | 40,000 | Small profits rate | 7,600 | 19.0% |
| B: Mid-band with marginal relief | 120,000 | 125,000 | Marginal relief | 28,200 | 23.5% |
| C: Above upper limit | 300,000 | 300,000 | Main rate | 75,000 | 25.0% |
These examples show why a simple 19% versus 25% view is not enough. For many businesses, the marginal band applies for years and influences dividend policy, bonus timing, and investment decisions.
8) Real UK statistics for context
Marginal relief now operates in a period where corporation tax receipts are historically high. HMRC and government publications show a substantial rise in receipts after pandemic-era lows and rate changes.
| Tax Year | Approximate UK Corporation Tax Receipts | Context |
|---|---|---|
| 2020-21 | About £46 billion | Pandemic impact and weaker profits in many sectors |
| 2021-22 | About £63 billion | Recovery in company profitability |
| 2022-23 | About £84 billion | Strong rebound and higher taxable bases |
| 2023-24 | About £90 billion plus | New 25% main rate and ongoing profit growth in parts of the economy |
Rounded figures for context based on official UK publications. Use the latest HMRC bulletins for precise current totals.
9) Common calculation mistakes to avoid
- Using taxable profits instead of augmented profits when testing limits.
- Forgetting exempt distributions that affect augmented profits.
- Ignoring associated companies when applying thresholds.
- Failing to pro-rate limits for short periods.
- Applying relief outside the lower-to-upper band.
- Not reconciling tax computation to the CT600 period and basis.
Even a small error in associated company count can move a company from marginal relief to full main rate. That has a direct cash effect and can also distort quarterly instalment expectations for larger businesses.
10) Practical planning points for directors and finance teams
- Model profits quarterly. Marginal relief means incremental profits can have a higher marginal burden than expected.
- Track group structure changes. New entities and ownership shifts can alter associated company status.
- Assess timing of distributions and transactions. Period-end choices may influence augmented profits and relief.
- Document assumptions. Keep a clear schedule for exempt distributions and limit adjustments.
- Use sensitivity analysis. Test cases at key profit points like adjusted lower limit, midpoint, and upper limit.
This approach supports better dividend planning, more accurate cash forecasting, and fewer surprises at filing time.
11) Authoritative resources
12) Final takeaway
A robust uk corporation tax marginal relief calculation example always starts with the right inputs: taxable profits, augmented profits, associated company count, and period length. Once those are correct, the mathematics is straightforward. The strategic value comes from forecasting and scenario analysis, not just year-end compliance. Use the calculator above to test your figures quickly, then confirm treatment with your tax adviser where group complexity, distributions, or unusual transactions are involved.