UK Corporation Tax Marginal Relief Calculator 2024/25
Calculate Corporation Tax for FY 2024/25 using Small Profits Rate, Main Rate, and Marginal Relief for companies with profits between the lower and upper limits.
Formula used for marginal band: Corporation Tax = (Taxable Profits x 25%) – Marginal Relief, where Marginal Relief = (Upper Limit – Augmented Profits) x (Taxable Profits / Augmented Profits) x (3/200).
Tax Visualization
This chart compares tax under the 19% rate, 25% rate, and your calculated liability including marginal relief.
Expert Guide: UK Corporation Tax Marginal Relief Calculation 2024/25
From April 2023 onwards, UK Corporation Tax moved from a single headline rate to a tiered structure, and this continues into 2024/25. That change has made planning and compliance more technical for owner managed businesses, group companies, fast growing startups, and established trading companies alike. If your profits are not clearly below the lower limit or above the upper limit, you need to calculate marginal relief correctly. This guide explains the framework in practical terms and gives you a robust way to understand your likely tax position before filing your return.
For 2024/25, the key idea is simple: companies with low profits may still pay 19%, companies with higher profits pay 25%, and companies in between get relief so that the effective rate rises gradually rather than jumping straight from 19% to 25%. In practice, the detail is in the limits, augmented profits, associated company rules, and accounting period apportionment. Missing any of those can produce an incorrect result.
Current 2024/25 rate framework at a glance
The UK operates a three part approach for most companies:
- Small Profits Rate: 19% where profits are at or below the lower limit.
- Main Rate: 25% where profits are at or above the upper limit.
- Marginal Relief Band: profits between limits are taxed at 25% with relief deducted via a statutory formula.
The standard annual limits are:
- Lower limit: £50,000
- Upper limit: £250,000
These limits are reduced if either of the following applies:
- Your accounting period is shorter than 12 months.
- Your company has associated companies in the period.
| Band (FY 2024/25) | Profit condition | Corporation Tax treatment | Notes |
|---|---|---|---|
| Small profits | Augmented profits at or below adjusted lower limit | 19% of taxable total profits | Often used by micro and small companies with no associated entities |
| Marginal band | Between adjusted lower and upper limits | 25% less marginal relief | Effective rate rises gradually toward 25% |
| Main rate | Augmented profits at or above adjusted upper limit | 25% of taxable total profits | No marginal relief available above upper limit |
The formula behind marginal relief
HMRC applies a statutory fraction for marginal relief. For FY 2024/25, the standard fraction used in most calculations is 3/200. The practical formula is:
Marginal Relief = (Upper Limit – Augmented Profits) x (Taxable Total Profits / Augmented Profits) x (3/200)
Then:
Corporation Tax = (Taxable Total Profits x 25%) – Marginal Relief
There are two important terms here:
- Taxable Total Profits: the profits charged to Corporation Tax after tax adjustments.
- Augmented Profits: taxable total profits plus exempt distributions (in broad terms, relevant dividend type income used for limit testing).
Many businesses make errors by applying the formula to taxable profits but forgetting that band positioning is determined by augmented profits and adjusted limits.
Associated companies and why they matter so much
If your company has associated companies, your lower and upper limits are divided by the number of associated companies plus one. This can shift a business that seems clearly in small profits territory into the marginal or even main rate band.
Example concept:
- No associated companies: lower £50,000, upper £250,000.
- Two associated companies: divide by 3, so lower £16,666.67 and upper £83,333.33 (before any period apportionment).
This rule is a major driver of higher effective tax costs in groups and in structures with multiple companies under common control. Review associated company status annually, especially where ownership percentages, rights, or control relationships have changed.
Short accounting periods and time apportionment
If your accounting period is not exactly 12 months, the limits are proportionally reduced. For a 6 month period with no associated companies, the limits are effectively halved to £25,000 and £125,000. This catches many new incorporations and cessation periods where management assumes full year limits still apply.
In planning terms, this means timing around year ends can materially affect the rate mix and marginal band exposure. Businesses close to a threshold should model both taxable profits and augmented profits across alternative period lengths before making decisions.
Worked examples with practical interpretation
Below is a practical comparison showing indicative outcomes where there are no associated companies and a full 12 month period. The marginal relief examples assume augmented profits equal taxable total profits for simplicity.
| Taxable profits | Augmented profits | Band | Tax result | Effective rate |
|---|---|---|---|---|
| £40,000 | £40,000 | Small profits | £7,600 | 19.00% |
| £120,000 | £120,000 | Marginal band | Approx £26,850 | Approx 22.38% |
| £220,000 | £220,000 | Marginal band | Approx £53,100 | Approx 24.14% |
| £300,000 | £300,000 | Main rate | £75,000 | 25.00% |
These figures highlight the core effect of marginal relief: an effective rate that transitions from 19% toward 25%, rather than an abrupt cliff edge. However, the transition is sensitive to augmented profits and associated company adjustments.
Real UK statistics and market context
Corporation Tax is now one of the major UK tax receipts. HMRC and OBR publications show a substantial rise in receipts in recent years, driven by profit growth in some sectors, policy changes, and the increase in headline rate for larger profits.
| Fiscal year | Indicative UK Corporation Tax receipts (£bn) | Context |
|---|---|---|
| 2020/21 | Approx 48 | Pandemic period pressure on profits and tax base |
| 2021/22 | Approx 63 | Recovery and stronger business profitability |
| 2022/23 | Approx 81 | Strong receipts growth before full impact of new banding |
| 2023/24 | Approx 90 | Higher rates and resilient taxable profits |
| 2024/25 (forecast basis) | Approx 95 to 100 | Policy continuation with rate structure in place |
These broad official series levels are useful because they show why HMRC is increasingly focused on technical accuracy in Corporation Tax returns, including group relationships, profit allocation, and relief calculations.
Step by step method to calculate correctly
- Start with taxable total profits for the accounting period.
- Add exempt distributions to determine augmented profits.
- Compute adjusted limits:
- Apply time apportionment for months in period.
- Divide by associated companies plus one.
- Compare augmented profits to adjusted limits and identify the band.
- If in marginal band, apply the marginal relief formula using fraction 3/200.
- Calculate tax as 25% of taxable profits less marginal relief.
- Cross check effective rate and compare to expectation.
- Retain calculation evidence with your tax working papers.
Common mistakes businesses make
- Using taxable profits alone to determine band, ignoring augmented profits.
- Forgetting associated company limit reduction.
- Applying full year limits to short periods.
- Incorrectly assuming 19% applies to all profits once under £250,000.
- Missing data quality issues, especially where group structures changed mid year.
Practical warning: Marginal relief is a formula relief, not a separate tax rate you can apply as a flat percentage. If your model uses a single fixed rate for the marginal band, it can produce filing errors.
Planning opportunities without aggressive structuring
Good Corporation Tax planning is usually about clean forecasting and timing rather than artificial arrangements. Useful areas include:
- Forecasting augmented profits quarterly, not only year end taxable profits.
- Testing year end options where accounting period length changes tax thresholds.
- Reviewing capital allowance timing and investment strategy.
- Monitoring group company changes and control relationships.
- Ensuring dividend and exempt distribution data is correctly captured.
For boards and finance teams, scenario modelling is critical. A company near the upper limit can face a sharp increase in effective rate from relatively modest profit uplift, especially where associated companies reduce thresholds.
How to use the calculator above effectively
Enter taxable total profits, then add exempt distributions if relevant. Input the count of associated companies and the number of months in your period. The calculator then adjusts limits and applies the 2024/25 marginal relief methodology. You get:
- Adjusted lower and upper limits.
- Applicable tax band.
- Marginal relief amount, if available.
- Total Corporation Tax and effective rate.
- A chart comparing 19% baseline, 25% baseline, and calculated liability.
This gives you a finance ready estimate for budgeting and board reporting. For filing, always reconcile with your final tax computation and current HMRC guidance.
Authoritative references for compliance
Use official and high authority sources to validate assumptions, rates, and definitions:
- HM Government: Corporation Tax rates and allowances
- HMRC: Corporation Tax Marginal Relief guidance
- HMRC Company Taxation Manual: Marginal relief technical notes
Final thoughts for 2024/25
Corporation Tax in the UK is now more nuanced than it was under a single headline rate. For many companies, the key compliance risk is not arithmetic, it is classification and input quality: getting the right profit measure, the right limits, and the right group context. When those are correct, the formula is straightforward and repeatable.
If you are a director, finance lead, or adviser, treat marginal relief as a core part of quarterly tax forecasting, not just a year end clean up item. Doing so improves cash planning, avoids return errors, and helps you communicate realistic post tax profit outcomes to stakeholders.
Use the calculator as a practical first pass, then align results with your full tax computation, accounting disclosures, and any current year HMRC updates that apply to your circumstances.