Free tools
Free UK Corporation Tax tools
Work it out in a minute. Check every step.
Free calculators for directors of UK limited companies: work out your Corporation Tax deadlines and other company tax figures in a minute, with the rules explained and linked to GOV.UK. They work on this site, inside AI assistants and on your own website.
- 18 free tools, no sign-up
- Rules linked to GOV.UK
- Free to embed
Which free Corporation Tax calculators does Taxley offer?
Taxley's free calculators answer the Corporation Tax questions that directors of small UK companies ask most. Each one is listed below with what it works out. Every calculator shows a worked example, explains the rules with links to GOV.UK and gives you a link to your own result to save or share.
Tax and reliefs
What the company owes, and what brings it down.
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The Corporation Tax on one period's taxable profits.
- Marginal relief
- Associated companies
- Short periods
What it covers
Estimates the Corporation Tax a UK limited company pays on its taxable profits for one accounting period of up to 12 months. Applies the small profits rate, the main rate and marginal relief, with associated companies, short periods and periods that straddle 1 April. A close investment-holding company pays the main rate on all its profits. Returns the tax, the effective rate and the payment and filing dates.
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The s.455 tax on a director's loan still owed at the year end.
- Section 455
- Repaid within 9 months
- Due date
What it covers
Works out section 455 tax and repayment relief on a director's loan, with an optional beneficial-loan estimate using HMRC's normal averaging method, the director's marginal Income Tax rate and the company's Class 1A National Insurance.
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The capital allowances a company can claim for one period.
- Annual investment allowance
- Full expensing
- Pools
What it covers
Works out a UK limited company's capital allowances for one accounting period: the annual investment allowance, full expensing, the 50% and zero-emission car first-year allowances, and writing-down allowances at 14% (18% before 1 April 2026, a hybrid rate for a period spanning that date) and 6%. It also shows balancing charges and the pools carried forward.
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The gain or loss when a company sells land, buildings or shares.
- Indexation allowance
- Land and buildings
- Shares
What it covers
Works out a UK limited company's chargeable gain or allowable loss when it sells UK land or buildings, or shares it bought in one purchase, including indexation allowance frozen at December 2017. It shows the Retail Prices Index figures and factor used, and applies the rule that indexation can't create or increase a loss.
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The benefit-in-kind tax on a company car, and what the company saves.
- BiK %
- Electric cars
- Class 1A
- Capital allowances
What it covers
Works out the benefit in kind on a UK company car for 2025/26 or 2026/27: the appropriate percentage, the car and fuel benefit, the director's Income Tax and the company's 15% Class 1A National Insurance. It also shows the company's capital allowances or lease deduction and the Corporation Tax they save, for electric, hybrid, petrol and diesel cars.
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The van benefit and van fuel benefit, and the tax on them.
- Van benefit
- Fuel benefit
- Zero-emission vans
What it covers
Works out the benefit in kind on a UK company van for 2025/26 or 2026/27: the flat van benefit (nil for a zero-emission van), the van fuel benefit, the driver's Income Tax and the company's 15% Class 1A National Insurance, with the Corporation Tax the company saves on the van.
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Approved mileage, taxable excess and Mileage Allowance Relief shortfall.
- Cars and vans
- Motorcycles
- Mileage relief
What it covers
Calculates the HMRC approved mileage amount for an employee or director using their own car, van, motorcycle or bicycle for business travel, then shows the tax-free payment, taxable excess or Mileage Allowance Relief shortfall for 2025/26, 2026/27 or 2027/28.
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The homeworking flat rate and actual additional costs with records.
- £6 a week
- £26 a month
- Actual costs
What it covers
Calculates the £6 weekly or £26 monthly homeworking amount a limited company can pay a director or employee without evidence, and compares it with reasonable additional household costs supported by records.
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Whether a benefit passes the £50 conditions and director annual cap.
- £50 each
- £300 director cap
- Yes or no
What it covers
Checks whether one non-cash benefit costing £50 or less including VAT can qualify as a tax-free trivial benefit and, for a director of a close company, applies the £300 annual cap with a reason for every failed condition.
Deadlines and penalties
When to pay and file, and what filing late costs.
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Your payment date, CT600 deadline and accounts deadline.
- Payment date
- CT600 deadline
- Companies House
What it covers
Works out a UK private limited company's Corporation Tax payment date, CT600 filing deadline and Companies House accounts deadline from its accounting period. Accounts longer than 12 months are split into two Corporation Tax periods, each with its own payment date.
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HMRC's penalties for a late CT600, plus late payment interest.
- Flat penalties
- Tax-geared penalty
- Interest
What it covers
Works out HMRC's penalties for filing a UK company's Company Tax Return (CT600) late — the flat £200/£400 penalties for filing deadlines from 1 April 2026 (£100/£200 before then), and the 10% or 20% tax-geared penalty — plus late payment interest on the Corporation Tax at HMRC's published rates.
Company and accounts
Company size, long periods and the accounts file.
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Whether the company is a micro-entity, small, or neither.
- Micro-entity
- Small company
- 2-of-3 test
What it covers
Checks whether a UK private company is a micro-entity, small, or neither for a financial year under the Companies Act 2006, using the limits raised for years starting on or after 6 April 2025, the 2-of-3 test, turnover pro-rating for short or long years, and the two-consecutive-years rule.
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Splits accounts longer than 12 months into two CT600 periods.
- Two CT600s
- Profit split by days
- Both deadlines
What it covers
Splits UK company accounts covering more than 12 months (up to 18) into the two Corporation Tax accounting periods, with each period's dates, days, payment deadline and share of the profit by days, plus the CT600 filing deadline for both returns and the Companies House accounts deadline.
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Upload an iXBRL accounts file and get a plain-English list of problems.
- File upload
- Taxonomy check
- Deleted after the check
What it covers
Upload a company's iXBRL accounts or Corporation Tax computations file (.html or .xhtml) and get a plain-English list of any problems: file safety, iXBRL structure and, when available, full validation against the taxonomy it names. The file is checked and then deleted. Web page only, because it needs a file upload.
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Whether distributable profits cover a proposed dividend.
- Retained profits
- Section 830
- Shortfall
What it covers
Checks whether a UK limited company has enough estimated distributable profits for a proposed dividend, using retained profits brought forward, current profit after tax and dividends already paid, and shows any shortfall.
Paying yourself
Salary or dividends, pension contributions, and sole trader or company.
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The salary and dividend mix that leaves a director the most after tax.
- Salary vs dividends
- Dividend tax
- Employment Allowance
What it covers
Finds the salary and dividend mix that leaves a UK limited company director the most from the year's profit, searching every salary to the penny (a usual salary level is shown when it comes within £1 of the best), and compares it with no salary, £5,000, the lower earnings limit, £12,570 and your own figure, each with the rest paid as dividends. Works out Corporation Tax (with marginal relief), employer and employee National Insurance, the Employment Allowance, Income Tax and dividend tax for 2025/26 or 2026/27, and shows the best mix and the take-home pay of each.
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The tax on the same profit as a sole trader and as a limited company.
- Class 4 NI
- Corporation Tax
- Break-even profit
What it covers
Compares the tax on the same business profit as a UK sole trader (Income Tax and Class 4 National Insurance) and as a one-owner limited company paying out all its profit (Corporation Tax, National Insurance, Income Tax and dividend tax, with the salary that leaves the owner the most, to within £1), for 2025/26 or 2026/27. Shows the take-home pay each way and the profits at which the cheaper option changes.
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A company pension contribution against the same money as salary or dividends.
- Corporation Tax relief
- No National Insurance
- Annual allowance
What it covers
Compares a UK limited company paying an amount into the director's pension as an employer contribution with paying the same company money as extra salary or an extra dividend, for 2025/26 or 2026/27. Shows the Corporation Tax saved, the National Insurance avoided, the net amount into the pension and the take-home pay each other way, and checks the annual allowance (£60,000, tapered or the £10,000 money purchase allowance) against all the director's pension savings for the year.
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Beyond this site
The same calculators, with the same figures, on your website, in your own code, inside your AI assistant and in your browser.
Embed on your site
Are the calculators free to embed on my website?
Yes. Each calculator that doesn't need a file upload has an embed version you can place on your own website with a short snippet, free of charge. Please keep the plain link to the calculator that comes with the snippet, so your readers can see where the figures come from and check the full rules.
Copy the snippet from the "Embed this calculator on your site" box on each calculator's page, or from the embed section of the developer page. The calculator works on phones and without JavaScript.
Get the embed codeJSON API
Is there a free JSON API for the calculators?
Yes. Developers can send the same inputs to Taxley's free JSON API and get back the figures these pages show, with a plain-English answer, the sources and a link to the result. There is no key or account to set up, and an OpenAPI description lists each tool and the inputs it takes.
Start from https://taxley.co.uk/api/v1/tools, which lists every tool with its input schema.
Use in AI assistants (MCP)
Can AI assistants use these tools?
Yes. Assistants such as Claude and ChatGPT can call the calculators through Taxley's free Model Context Protocol (MCP) server, and developers can use the JSON API. Both give the same figures as these pages, with a link to the result, and need no key or account. The developer page explains how to set them up.
Add https://taxley.co.uk/mcp as a custom connector in your assistant, or read Taxley tools for developers and AI assistants for the steps, the API and the embed code.
Use it in Chrome
Is there a Chrome extension?
Yes. The free Taxley extension puts the deadline calculator and the Corporation Tax estimate in your browser toolbar. Enter the date your accounts end to see when to pay the tax, file the CT600 and file accounts at Companies House, and save the dates to your calendar.
It asks for no browser permissions and gives the same figures as these pages.
Get the Chrome extensionFrequently asked questions
Are Taxley's calculators really free?
Yes. The calculators, the embeds, the JSON API and the MCP server are free to use, with no account and no key. We only ask that you link to taxley.co.uk when you publish a result, so readers can see how it was worked out.
Does Taxley save the figures I enter?
No. The figures you enter are used to work out the answer and are not saved to an account or a database. A result link simply carries your inputs in the web address, so anyone you share it with sees the same result.
Is a calculator result tax advice?
No. The calculators give general guidance based on the rules HMRC and Companies House publish on GOV.UK. They can't see your company's full circumstances, so check the figures against your own records before you file or pay.
How are the calculators kept accurate?
Each calculator applies the published rules to the figures you enter and says what it doesn't cover. We check the rules against GOV.UK, show the date of the last review on each page and link to every source, so you can follow each step yourself.
Can I file my Company Tax Return with Taxley?
Yes. Taxley is software for directors of small limited companies to prepare their CT600 and iXBRL accounts, file the return to HMRC and file the accounts at Companies House. Preparing and previewing a return is free; you pay one fee when you choose to file.
Last reviewed . The calculators give general guidance, not tax advice.
When your figures are ready
File your company tax return with Taxley
Taxley prepares your CT600, tax computation and iXBRL accounts, files the return to HMRC and files the accounts at Companies House. Preparing a return is free; you pay one fee from £9.50 when you choose to file. No VAT to add.