Corporation Tax Calculator — UK CT 2026/27
UK Corporation Tax calculator
Estimate your limited company’s Corporation Tax liability using 2026/27 rates. Includes the small profits rate (19%), main rate (25%), and marginal relief between £50,000 and £250,000 — plus the threshold split for associated companies and short accounting periods.
Calculate your CT bill
2026/27 rates: 19% small profits to £50,000; 25% main rate at £250,000+; marginal relief between (effective ~26.5%). Thresholds are split equally across associated companies (sister companies under common control) and pro-rated for accounting periods shorter than 12 months.
How Corporation Tax works
UK Corporation Tax was reformed in April 2023 — the previous flat 19% was replaced with a tiered system. Today there are three effective rates depending on profit level:
- Small profits rate — 19% on profits up to £50,000. Most owner-managed companies sit here.
- Main rate — 25% on profits at or above £250,000.
- Marginal relief band — profits between £50,000 and £250,000 are taxed at the main 25% with a sliding-scale credit, giving an effective rate of 26.5% on profits in that band. (Yes, the marginal rate is higher than the main rate — that’s the design.)
The £50,000 and £250,000 thresholds are shared between associated companies. If you control three companies, each gets a £16,666 small-profits threshold and a £83,333 marginal upper limit. This catches a lot of group structures by surprise.
Thresholds are also pro-rated for short accounting periods. A 6-month period halves the £50k and £250k limits.
Frequently asked questions
Why is the marginal rate 26.5% when the main rate is only 25%?
Because of how marginal relief works mechanically. Above the £250k upper limit you pay 25% on everything. In the marginal band you pay 25% on every pound, then get a credit on the difference between profit and the upper limit. The effective rate climbs from 19% (at £50k) to 26.5% as profits approach £250k — then drops back to 25% above. It’s an odd shape but that’s the legislation.
Who counts as an “associated company”?
Any company under your common control with another. Specifically: companies you and any associates (spouse, business partner) hold 50%+ in. Dormant companies and pure passive holding companies are usually excluded. Subsidiaries inside a 75% group also count. Get this wrong and you can end up paying the marginal rate when you thought you were on small profits.
What expenses can my company deduct?
Anything wholly and exclusively for the trade — staff costs (including employer NIC), rent, utilities, software, professional fees, depreciation (via capital allowances on equipment), bank interest, marketing. Entertaining clients is usually NOT deductible. Director’s pension contributions and salary are deductible. We send a checklist when you sign up.
When is Corporation Tax due?
Nine months and one day after the end of your company’s accounting period. The CT600 return is due 12 months after the period end. So a 31 December year-end means CT is due 1 October the following year, with the return by 31 December the year after. If profits are over £1.5m, instalment payments apply earlier.
What if I leave profit in the company instead of drawing it?
The company still pays Corporation Tax on it — that’s unavoidable. But you only pay personal tax (income tax / dividend tax) when you draw it. So leaving profit in the company defers personal tax and gives you flexibility for future drawdown, pension contributions, or eventual exit (potentially via Members’ Voluntary Liquidation with BADR, currently 18%).
Can I claim R&D tax relief?
Yes — and the rules changed in April 2024. There’s now a single merged scheme combining the previous SME and RDEC schemes for most claimants, plus a separate enhanced rate for “R&D-intensive” loss-making SMEs. We assess R&D claims for clients who do qualifying technical work and prepare the additional information form (AIF) HMRC now requires.
Want this calculated and filed properly?
The calculator handles the headline numbers. The actual CT bill depends on capital allowances, R&D claims, group relief, dividends paid, associated companies and pension timing — we look after all of it on a fixed annual fee.