The Most Accurate Corporation Tax Calculator UK

Corporation Tax

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Net Profit

£0

Your Details

£100,000 Profit
Profit Breakdown
Tax vs Net Profit
Estimate based on entered Corporation Tax Rate

Corporation tax shouldn’t be a guessing game or a sweaty spreadsheet at 1 a.m. FinCalc’s Corporation Tax Calculator shows a clean, defensible number in minutes, starting from accounting profit, reconciling to taxable profit, then applying the correct rate logic (small profits, main rate, or marginal relief) for your period and company profile. No hand-waving, no “trust us,” just a transparent ladder from P&L to tax due.

 

Plug in revenue, costs, capital purchases, and any quirks (client entertainment, car purchases, director salary, employer pension). The Corporation Calculator automatically handles add-backs, capital allowances, and relief timing, then lets you spin scenarios: “What if we expense a laptop this year?”, “What if we pay a director’s pension pre-year-end?”, “What if we split the trade across associated companies?” You’ll see the tax movement and the cash impact instantly.

How to use the Corporation Tax Calculator?

Start simple, then refine. You are moving from accounting profit to taxable profit, then applying the right rate logic. Run a clean baseline first in the Corporation Tax Calculator, save it, and only then layer optimisations like capital allowances, pensions, and marginal relief.

Enter the basics

Set your company’s year start and end dates so thresholds and any short-period rules are correct. Enter trading revenue and ordinary operating costs as they appear in your P&L, wages, rent, software, utilities, and marketing. Keep these pre-tax and pre-adjustment for a clean baseline. If you have non-trading income, interest, property, or chargeable gains, add those in their own boxes so the calculator can route them correctly. Got VAT in the mix? Use the VAT Calculator to price quotes VAT-inclusive vs VAT-exclusive without wrecking margins. 

Adjust for tax

Now reconcile from accounting to taxable profit. Add back items that are not deductible for corporation tax client entertainment, fines, most depreciation, and certain provisions. Replace depreciation on plant and machinery with capital allowances by listing qualifying assets and their pools. If you have R&D style incentives or other reliefs, leave them for later toggles. The first pass should prove the baseline before incentives.

Pick the right rate logic

Choose whether you expect to sit in small-profits, main rate, or the marginal relief zone. The Corporation Tax Calculator will auto-determine this once it knows your augmented profits and any associated companies, but set your expectation here so you can compare. If you have associated companies or a short period, enter them; the thresholds will scale and may move you into marginal relief or main rate sooner.

Add director pay, pensions, and dividends

Model extraction choices before year-end. In Scenario A, set a director’s salary and an employer pension contribution paid by the company; these reduce taxable profits and often beat a late dividend for cash efficiency. In Scenario B, a lower salary and an increase in dividends result in the corporation tax rising, but personal tax falls or rises depending on bands. Save both scenarios. The Corporation Calculator will show corporation tax due, post-tax profit, and an owner’s after-tax cash flow so you can select the mix that protects cash flow and keeps HMRC quiet. Price the owner’s cash precisely: pair salary through PAYE with the PAYE Tax Calculator and dividends with the Dividend Tax Calculator. 

What counts as profit?

Your accounts show accounting profit. HMRC taxes taxable profit. The gap between the two is where most mistakes and cash leaks happen. The Corporation Tax Calculator makes that bridge explicit so your CT number is defendable, not a late-night guess.

Accounting profit vs taxable profit: the reconciliation ladder

Start with your P&L operating profit. Then walk the reconciliation ladder in the calculator.

  1. Add back items that are not tax-deductible.
  2. Remove accounting charges that are replaced by tax rules for capital.
    Include income and gains that sit outside trading if they are taxable.
  3. The result is taxable total profits for the period. Only then do we apply the correct rate logic: small profits, marginal relief, or main rate. The ladder view in the Corporation Tax Calculator shows every step, so the final figure can be traced line by line from your accounts.

Add backs and deductions, what actually moves the number

Common add-backs include client entertainment, most fines and penalties, depreciation on plant and machinery, certain general provisions, and non-business elements of costs. These inflate accounting profit for tax purposes because HMRC does not allow them as deductions. Common deductions and swaps depreciation is replaced by capital allowances on qualifying assets, plant, machinery, integral features, and eligible fixtures. Some accruals reverse if they never crystallise. Where expenditure is partly private, only the business portion is allowed. The calculator lists typical categories so you tick items, not chase spreadsheets.

Relevant income streams, trading property, and chargeable gains

Not all profit is created equal.
 • Trading income is your core business profits after allowable expenses.
 • Property business rental profits in the company sit alongside trading but may have different adjustments.
 • Chargeable gains on disposals of assets feed into taxable total profits after indexations or reliefs where applicable.
 Enter each stream in its own box. The Corporation Calculator routes them correctly, applies reliefs in the right order, and shows one coherent taxable total. Result clarity on what HMRC is actually taxing and why your corporation tax due lands where it does.

Allowable vs disallowable expenses

Expenses decide your tax, not just your revenue story. Get the treatment wrong and you’ll either overpay corporation tax or build a nasty HMRC surprise. Use the Corporation Calculator to separate what’s deductible from what must be added back, then watch the cash move in real time.

Staff costs, director salary, subcontractors

Payroll costs tied to running the trade are usually allowable: employee wages, employer NICs, statutory pension contributions, and training that maintains existing skills. Director salaries are deductible when they reflect genuine work; if you pay yourself, model a salary in the Corporation Tax Calculator alongside an employer pension to see how it reduces taxable profit. Subcontractors are generally allowable where the engagement is wholly for the trade, keep contracts/invoices tidy, and remember that “disguised employment” risks can reclassify costs. Recruitment fees for business roles are typically fine; termination payments have nuanced rules, model, then sanity-check with your accountant before you commit.

Travel, subsistence, home-office, phones, software

Travel and subsistence are allowable when they’re wholly and exclusively for business (no private detours). Regular commuting to a permanent workplace is not; temporary workplace rules are different, be disciplined with evidence. Home-office costs can be apportioned on a fair, consistent basis (space × time × cost method is common). Mobiles and broadband: claim the business proportion, or route through company contracts where usage is demonstrably business-first. Software subscriptions, cloud tools, and domain/hosting are usually deductible; licences linked to capital items (e.g., perpetual software bundled with equipment) may need capital treatment, use the calculator’s capital vs revenue toggle to avoid muddying relief.

Client entertainment, gifts, fines

Client entertainment is the classic trap: it’s not deductible for corporation tax, full stop, add it back. Gifts with a clear promotional purpose, modest cost, and no food/drink angle may qualify; anything that looks like hospitality usually won’t. Fines and penalties are generally disallowable; late filing charges and parking penalties rarely fly. Political donations and most charitable payments need special handling (company donations to registered charities can be deductible, but outside the trading computation). In the Corporation Tax Calculator, tick these as disallowable so your accounting profit reconciles to taxable profit without wishful thinking.

Provisions, accruals, “capital vs revenue” tests

General provisions (big-bath reserves, vague contingencies) are red flags; HMRC expects specificity. Only accrue what is probable and reliably measurable; doubtful debts tied to real invoices are different from blanket percentages. Repairs that restore an asset are typically revenue (deductible); enhancements that improve or extend life are capital (relief via capital allowances, not an immediate deduction). Upfront fees that create enduring benefit (patents, trademarks, some implementation projects) may require capitalisation.

Capital allowances & investment planning

Capex is where accounting depreciation meets tax reality. For corporation tax, you don’t deduct depreciation;  you claim capital allowances. The Corporation Tax Calculator swaps book depreciation for the correct relief (AIA, full expensing, WDAs), so you see cash tax movement, not just tidy accounts. Use this section to time purchases and pick the pool that maximises relief.

AIA & WDA (plant & machinery the right way)

Annual Investment Allowance (AIA) gives up to a set limit of 100% deduction for qualifying plant and machinery in the year of purchase. Above that, or where AIA isn’t available, you move to Writing Down Allowances (WDA) across the main pool or special-rate pool. In the Corporation Calculator, list each qualifying asset (or totals by pool), and we automatically:

  • Remove book depreciation;
  • Apply AIA first (until exhausted);
  • Carry the balance to the main or special pool and compute WDA.
  • Bring forward any unrelieved pool balances to next year’s scenarios.

Result: a clean reconciliation from accounting to taxable profit with the right-year relief. Want the effective rate after allowances? Snapshot post-relief profit here, then preview the owner’s personal bands with the Income Tax Calculator.

Cars & CO₂ rules (pooling and restricted relief)

Cars are special. Relief depends on CO₂ emissions and whether the vehicle is a car (restricted) or van/qualifying truck (usually plant & machinery). Low/zero-emission cars can access enhanced reliefs, while higher-emission cars generally fall into the special-rate pool with slower relief. Lease payments on cars also have restrictions. In the Corporation Tax Calculator, pick “car” vs “van/other,” enter CO₂, and we route to the right treatment automatically, preventing the classic mistake of claiming AIA on a car that doesn’t qualify.

First-year/temporary incentives

When first-year incentives (like full expensing for companies on qualifying main-rate assets, and enhanced first-year allowances for some special-rate items) are available, timing matters. Buying one day before year-end can compress relief into the current period and reduce corporation tax immediately; buying one day after pushes relief into next year. Toggle “first-year allowance/full expensing” on the asset row, and the Corporation Tax Calculator will:

  • Prioritise the enhanced rate where conditions are met.
  • Fall back to AIA/WDA if not.
  • Show your effective CT rate movement so you can judge if accelerating spend actually helps cash.

Fixtures, integral features, and practical record-keeping

Shop fits, air-con, wiring, lifts, and other integral features often belong in the special-rate pool. Fixtures in property purchases require s.198 elections or fixed value agreements to lock the basis for allowances, lose the paperwork, lose the relief. Best practice:

  • Keep invoices specific (split labour, fixtures, and equipment lines);
  • tag assets to the correct pool at purchase;
  • Maintain a capex register with dates in service (not just invoice dates).

Enter totals by pool or individual assets in the Corporation Tax Calculator; we show the allowance taken this year, the pool carried forward, and the impact on Corporation Calculator outputs like taxable profits, CT due, and effective rate.

Extracting profits, salary, dividends, pensions

This is where strategy beats spreadsheets. How you extract profits changes both the corporation tax and the owner’s after-tax cash. Use the Corporation Tax Calculator to price each route: salary (deductible, but brings PAYE/NIC), dividends (not deductible, taxed personally), and employer pensions (deductible, powerful, but locked until pension age).

Director salary vs dividend

Salary is a trading expense, so it reduces taxable profits and therefore corporation tax. The trade-off is PAYE Income Tax plus employee and employer NIC, and cash leaving the company immediately. Dividends are paid from post-tax profits; they do not reduce corporation tax, but can be more efficient for the shareholder depending on personal bands and other income.
 In the Corporation Calculator, set Scenario A with a lean salary (ensure NI credit level if you want state pension years) and the balance as dividends. Then set Scenario B with a higher salary (or a one-off bonus) and lower dividends. The tool will show CT due (lower if salary/bonus is higheremployer NIC cost,
distributable reserves left for dividends, and Shareholders’ personal tax on dividends/salary. Read the owner’s net cash at the bottom, not just the CT headline.

 

Employer pension contributions

Company contributions to a director’s pension are generally deductible if they’re wholly and exclusively for the trade (commercially reasonable for the business size/profit). They reduce taxable profits (and so CT), avoid employee NIC, and don’t count as dividends. The trade-off is liquidity: the money is in a pension wrapper until access age and is subject to annual allowance rules.
 Model this in the Corporation Calculator by adding an employer pension contribution line. You’ll see  CT fall (because profits drop), no employee NIC on that amount, the company’s cash outflow vs the shareholders’ deferred benefit, and whether the contribution nudges you below a marginal-relief cliff (often improving the effective CT rate as well as the cash bill). If you were about to pay a dividend to fund a personal pension, compare a company-paid contribution instead; the calculator will usually show stronger total-system efficiency.

Scenario testing

Profit extraction is not one-size-fits-all. Build three quick cases:

A, Dividend-heavy: low salary (enough for NI credits if desired), no employer pension, rest as dividends.
B Balanced salary: moderate salary/bonus to reduce CT, plus a measured dividend.
C, Pension-led: lean dividend, company pays a chunky employer pension pre-year-end to drop profits.
 For each case, the Corporation Tax Calculator outputs: CT due, post-tax profit, dividends available, personal tax, and the owner’s after-tax cash. Pick the configuration that maximises owner net within your liquidity and compliance constraints.
Operator checklist: sanity-check associated companies (thresholds), confirm period dates (short period effects), make sure director salary reflects real work, and keep pension contributions commercially reasonable.

Compliance, payments & deadlines

Great numbers die in bad administration. Keep filings clean, dates locked, and payments predictable so your forecast isn’t nuked by interest or penalties. The Corporation Tax Calculator pairs the tax number with a light-touch checklist so you close the loop, compute, file, pay, and move on.

CT600, iXBRL, accounts approval, and the filing workflow

Your corporation tax return is the CT600 with tagged computations in iXBRL. The clean workflow is simple:

  1. Finalise statutory accounts and get board approval/minutes.
  2. Reconcile from accounting profit to taxable total profits (add-backs, capital allowances, reliefs) inside the Corporation Calculator and export the ladder for your working papers.
  3. Prepare iXBRL-tagged accounts and computations; attach to the CT600 and submit via HMRC’s portal or your tax software.
  4. Cross-check associated companies, short-period flags, and any marginal relief calculation in the return matches the calculator’s regime selection.

Keep your evidence: capex schedule, s.198 elections for fixtures, entertainment add-backs, car CO₂ data, pension payments cleared before year-end. Boring files beat exciting HMRC letters.

Payment timing

Cash control starts with dates:

  • Standard rule: corporation tax is usually due nine months and one day after the end of your accounting period; the CT600 filing deadline is typically twelve months after period end. Plan both.
  • Large/very large companies: if profits cross the “large” thresholds (adjusted for associated companies and short periods), tax is paid in instalments during the year. As a rule of thumb:
  • Large: four payments broadly around months 7, 10, 13, 16 from the start of the period.
  • Very large: earlier schedule, broadly months 3, 6, 9, 12.

Interest, penalties, and keeping HMRC letters boring

HMRC charges interest on late-paid corporation tax (it’s not deductible), and applies penalties for late filing or careless/inaccurate returns. Practical playbook:

  • Lock a payment calendar the day you close your forecast; set internal deadlines a week earlier than statutory dates.
  • Re-run the Corporation Tax Calculator when material events happen, new car benefit, big asset purchase, loss carry-back, group surrender, so instalments or the final payment are true up before the due date.
  • If you discover an error, correct it fast. Voluntary, timely corrections generally land softer than HMRC finding it first.

Accuracy & methodology

No black boxes here. FinCalc’s Corporation Tax Calculator shows every rung from accounting profit to tax due, then overlays rate logic, allowances, and reliefs so you can audit the result line-by-line. Use this section as your source of truth for how the engine works and how to sanity-check it fast.

What the calculator assumes?

  • Active rules & year: We run the current tax year logic you select, including rate bands, marginal-relief formula, associated-company scaling, and short-period pro-rating.
    Accounting tax bridge: Book depreciation is swapped for capital allowances (AIA/full expensing/WDA); disallowables (e.g., client entertainment, fines) are added back; qualifying deductions remain.
    Profit tests: We compute taxable total profits and augmented profits to place you in small-profits, marginal relief, or main rate.
    Rounding & presentation: We round to the nearest penny; totals reconcile to parts. Pools and loss balances carry forward between scenarios, so planning is apples-to-apples.

 

Conclusion

Clarity beats spreadsheets at 1 a.m. FinCalc’s Corporation Tax Calculator turns your accounts into a transparent, defendable tax position, fast. Start with accounting profit, reconcile to taxable profit with add-backs and capital allowances, then let the engine apply the correct rate logic (small-profits, marginal relief, or main rate) after scaling thresholds for associated companies and short periods. 

 

From there, pressure-test real decisions: time capex, carry back losses, allocate group relief, or swap a dividend for an employer pension. The result isn’t just a corporation tax figure; it’s a cash plan you can run the business on. No black boxes. No guesswork. Just a clean ladder from P&L to tax due, plus scenario testing that shows the owner’s after-tax cash. Ship year-end with CFO-level confidence.



FAQs

Does the Corporation Tax Calculator handle marginal relief?

Yes. It computes taxable and augmented profits, scales thresholds for associated companies and short periods, then applies the marginal-relief formula to show notional main-rate tax, relief deducted, and final corporation tax due.

Absolutely. Enter your associated-company count, and the Corporation Tax Calculator immediately adjusts lower/upper limits and reselects small-profits, marginal, or main rate, so you see regime flips before they become expensive.

Client entertainment and most fines are disallowable. The Corporation Tax Calculator treats them as add-backs, so accounting profit reconciles cleanly to taxable profit.

Thresholds pro-rate to your actual period length. Set start/end dates and the calculator time-apportions limits and payments so you don’t rely on full-year thresholds by mistake.

Yes. Enter your trading loss and choose carry-back (potential CT refund) or carry-forward (future offset). The Corporation Tax Calculator shows cash-now vs cash-later, plus effective-rate impact.

It does. Allocate current-period losses to profitable group members and watch each entity’s corporation tax and the group’s total cash bill update in real time.

Yes. Create scenarios with different salary/bonus, employer pension, and dividends. The Corporation Tax Calculator outputs CT due, distributable reserves, personal tax, and owner after-tax cash.

Book depreciation is replaced with capital allowances (AIA, full expensing, WDAs). You’ll see the swap on the reconciliation ladder and the cash effect on corporation tax.

Toggle company size and associated companies; the calculator surfaces standard due dates or QIP schedules so finance can plan cash without guesswork.

Yes. Input trading, property, and gains separately. The Corporation Tax Calculator routes each correctly and applies reliefs in the right order to produce one coherent taxable total.