UK Corporation Tax Rates 2023/24 Calculator
Estimate corporation tax for Financial Year 2023 using the small profits rate, main rate, and marginal relief rules.
Results
Enter your figures and click Calculate Corporation Tax.
This calculator is for UK Financial Year 2023 rates (effective from 1 April 2023). For complex cases, ring fence profits, very long periods, or group structures, confirm with a qualified tax adviser.
Expert guide: how to use a UK corporation tax rates 2023/24 calculator correctly
If you are searching for a reliable uk corporation tax rates 2023/24 calculator, you are usually trying to answer one of three practical questions: how much tax your company owes, which tax rate band applies, and whether marginal relief lowers the bill between the lower and upper limits. The 2023/24 period is especially important because the UK moved from a single corporation tax rate to a tiered structure for most companies. That means your estimate can be wrong by a meaningful amount if you rely on old 19 percent assumptions, ignore associated companies, or forget to apply augmented profits correctly.
From 1 April 2023, the headline system for most UK companies became: 19 percent small profits rate, 25 percent main rate, and marginal relief in between. This is straightforward in principle, but detail matters. A premium calculator should request taxable total profits, accounting period length, number of associated companies, and augmented profits. Those are not optional extras. They are the ingredients that decide your effective rate and final tax charge.
2023/24 corporation tax framework at a glance
The UK corporation tax regime for Financial Year 2023 is built around a lower threshold and an upper threshold. Companies with profits at or below the lower threshold normally pay 19 percent. Companies at or above the upper threshold normally pay 25 percent. Companies between those points can claim marginal relief, which smooths the jump between the two rates.
| Measure | Until 31 March 2023 | From 1 April 2023 (FY 2023) | Why it matters in a calculator |
|---|---|---|---|
| Main corporation tax rate | 19% | 25% | Defines tax for profits above upper limit |
| Small profits rate | Not separate | 19% | Applies at or below lower limit |
| Lower profits limit | Not used in same way | £50,000 | Starting point for marginal relief band |
| Upper profits limit | Not used in same way | £250,000 | End point for marginal relief band |
| Marginal relief standard fraction | Not applicable in this form | 3/200 | Required for precise mid band calculation |
The formula your calculator should use
A high quality calculator should mirror HMRC mechanics. For companies in the marginal relief band, tax is normally computed as:
- Corporation tax = Taxable profits × 25% − Marginal relief
- Marginal relief = (Upper limit − Augmented profits) × (Taxable profits / Augmented profits) × (3/200)
If taxable profits are at or below the lower limit, tax is typically 19 percent of taxable profits. If taxable profits are at or above the upper limit, tax is typically 25 percent of taxable profits. Limits are reduced for short accounting periods and also divided where associated companies exist.
Associated companies and why many estimates are too low
One of the most common errors in do it yourself tax estimates is ignoring associated companies. The lower and upper limits are divided by the number of associated companies plus your own company. For example, if your company has two associated companies, the divisor is three. That changes limits from £50,000 and £250,000 to £16,666.67 and £83,333.33 for a full 12 month period. As a result, companies can enter the 25 percent environment much earlier than expected.
| Associated companies | Divisor used | Adjusted lower limit (365 day period) | Adjusted upper limit (365 day period) |
|---|---|---|---|
| 0 | 1 | £50,000 | £250,000 |
| 1 | 2 | £25,000 | £125,000 |
| 2 | 3 | £16,666.67 | £83,333.33 |
| 4 | 5 | £10,000 | £50,000 |
Augmented profits: the hidden input that affects marginal relief
In simple cases, augmented profits equal taxable profits. In more complex cases, augmented profits can differ, often due to exempt distributions and other factors in the statutory calculation. If augmented profits are higher than taxable profits, marginal relief can be smaller than you first expect, increasing tax due versus a naive estimate. A robust calculator therefore lets you switch between a basic mode where augmented profits equal taxable profits and an advanced mode where you enter augmented profits separately.
Step by step process for calculating 2023/24 corporation tax
- Confirm your accounting period days, up to 365 for a standard short period adjustment.
- Input taxable total profits for that period.
- Set associated companies count and apply the divisor.
- Scale lower and upper limits by days and divisor.
- Choose augmented profits mode and enter value if separate.
- Apply 19 percent, 25 percent, or marginal relief formula depending on the band.
- Review effective tax rate and post tax profits.
- Cross check with your draft CT600 workings before filing.
Worked examples
Example A: small profits case. A company has £40,000 taxable profits, no associated companies, and a full year. The lower threshold is £50,000, so corporation tax is £7,600 at 19 percent.
Example B: marginal relief case. A company has £120,000 taxable profits, no associated companies, and augmented profits also £120,000. This falls between £50,000 and £250,000, so marginal relief applies. Main rate computation gives £30,000, marginal relief then reduces that amount, producing an effective rate between 19 and 25 percent.
Example C: associated company impact. A company has £120,000 profits but also one associated company. Limits become £25,000 and £125,000. The company now sits near the top of the marginal band, much closer to 25 percent tax than in the no association case.
Common mistakes when using a uk corporation tax rates 2023/24 calculator
- Using an old single rate calculator that assumes 19 percent for all profits.
- Ignoring associated companies and overstating thresholds.
- Using turnover instead of taxable total profits.
- Not adjusting thresholds for short accounting periods.
- Assuming augmented profits always equal taxable profits in every case.
- Treating calculator output as a filing substitute instead of a planning estimate.
Planning implications for directors and finance teams
The 2023/24 structure makes profit timing, remuneration strategy, and group structuring more sensitive than under a flat rate system. Forecasting quarterly or monthly is now valuable because crossing a threshold can increase the effective tax rate. Companies should also evaluate the relationship between investment allowances, salary and bonus planning, pension contributions, and group relief usage. A calculator cannot replace full tax planning, but it gives finance teams an immediate view of how scenario changes alter expected liability and post tax cash.
For boards and owner managed businesses, the practical benefit is better decision speed. If you can model outcomes at £70,000, £110,000, £160,000, and £300,000 projected profits, you can estimate tax cash needs and dividend capacity much earlier in the year. That can materially improve working capital planning and avoid surprises near filing deadlines.
Filing and payment context
Corporation tax payment deadlines and return deadlines still matter just as much as getting the rate correct. Most companies pay corporation tax 9 months and 1 day after the end of their accounting period. The CT600 is typically due 12 months after the period end. Large companies can be subject to instalment rules, which require earlier cash planning. Always align calculator outputs with your compliance timetable so forecast and payment behavior match.
Authoritative references for 2023/24 corporation tax
- UK Government: Corporation Tax rates and allowances
- HMRC guidance: Corporation Tax marginal relief
- UK Legislation: statutory tax framework
Final takeaway
A dependable uk corporation tax rates 2023/24 calculator should not only apply 19 percent and 25 percent rates. It must also handle marginal relief, adjusted thresholds, associated companies, and short periods. If those components are present, your estimate will be materially closer to the final filing position and far more useful for management decisions. Use calculator outputs to inform planning, then validate the final numbers through full accounts and tax computations before submission.