How to Use Outside IR35 Calculator
The Outside IR35 Calculator helps UK contractors estimate annual revenue, company profit, taxes, and personal take-home income from an Outside IR35 contract. Enter your day rate, working days per week, expected working weeks per year, business costs, accounting fees, pension contributions, salary extraction, and dividend extraction.
Choose the tax year and currency symbol, then review the right-hand result panel. The Outside IR35 Calculator shows annual contract revenue, average monthly revenue, deductible costs, corporation tax, post-tax company profit, salary, dividends, personal income tax, National Insurance, dividend tax, final take-home income, monthly take-home income, and effective tax rate.
Formula & Theory - Outside IR35 Calculator
The Outside IR35 Calculator applies a simplified limited company model:
Annual contract revenue = Day rate × Working days per week × Working weeks per year
Profit before corporation tax = Annual contract revenue - Deductible business costs - Salary - Pension
Corporation tax = Profit before corporation tax × Corporation tax rate
Post-tax company profit = Profit before corporation tax - Corporation tax
Final take-home = Salary + Dividends - Income tax - National Insurance - Dividend taxOutside IR35 generally means the contractor is treated as genuinely self-employed for the engagement and can operate through a limited company, subject to the contract and working practices supporting that status. A salary plus dividends strategy may be tax efficient when properly planned, but it depends on current UK tax rules, allowances, thresholds, and personal circumstances.
Assumptions and Limits
This calculator is deliberately simplified. It does not model VAT, flat-rate VAT, student loans, Scottish income tax differences, employer National Insurance, benefits in kind, director loan accounts, retained profits across years, spouse shareholding, or every corporation tax marginal relief detail. It is not tax advice.
Use Cases for Outside IR35 Calculator
The Outside IR35 Calculator is useful for contract planning and comparing commercial scenarios.
- Rate negotiation - Translate a day rate into annual and monthly income.
- Cost planning - See how expenses, accounting fees, and pension contributions change profit.
- Extraction strategy - Compare salary and dividend assumptions.
- Tax review - Estimate corporation tax, income tax, National Insurance, dividend tax, and effective rate.
Use the Outside IR35 Calculator before speaking with an accountant, then replace assumptions with your accountant’s tax-year-specific guidance.