Self-Employed Expenses Calculator
Calculate your allowable business expenses, compare simplified vs actual costs for vehicles and home office, and see exactly how much tax you save by claiming expenses for 2025/26.
Try another scenario
How to Use This Calculator
My Expenses tab
Enter your annual turnover and break down your business expenses into the main HMRC categories: office costs, travel, home office, marketing, professional fees, capital allowances, staff costs, and financial costs. The calculator shows your total allowable expenses, taxable profit, and how much tax and NI you save by claiming those expenses.
Simplified vs Actual tab
Enter your annual business miles and your actual vehicle running costs (fuel, insurance, repairs, depreciation, parking). The calculator compares the HMRC simplified mileage rate (45p for the first 10,000 miles, then 25p) against your actual costs, and shows which method gives you a larger deduction and tax saving.
Home Office tab
Enter your hours worked from home per week, the number of rooms used for business, and your household costs (rent, utilities, broadband, insurance, council tax). The calculator compares the HMRC flat rate method (£10-£26/month) against the actual proportion method, showing which saves you more.
Share your result
Every input is encoded in the URL. Click Share to send your exact scenario to an accountant, business partner, or save it for later.
The Formula
Self-employed expenses reduce your taxable profit, which in turn reduces both income tax and National Insurance:
Tax Saving = (Tax on full turnover) − (Tax on reduced profit)
Simplified Mileage:
• 45p per mile × first 10,000 business miles
• 25p per mile × miles above 10,000
Home Office Flat Rate:
• 25–50 hours/month = £10/month (£120/year)
• 51–100 hours/month = £18/month (£216/year)
• 101+ hours/month = £26/month (£312/year)
Home Office Actual Proportion:
Deduction = Total household costs × (Business rooms ÷ Total rooms)
Every £1 of allowable expenses reduces your tax bill by your marginal rate. For a basic rate taxpayer (20% income tax + 6% Class 4 NI), each £1 of expenses saves 26p in tax. For a higher rate taxpayer, each £1 saves 42p (40% + 2%).
The Annual Investment Allowance (AIA) lets you deduct up to £1,000,000 of qualifying equipment and machinery purchases in the year you buy them. Cars are excluded from AIA but can be claimed through capital allowance pools.
Example
Tom — Self-Employed Plumber, Birmingham
Tom is a self-employed plumber with £45,000 annual turnover. He drives 15,000 business miles per year and works from home 2 days a week managing invoices and quotes. He needs to decide between simplified and actual expenses for his van and home office.
Vehicle: Simplified vs Actual
Home Office: Flat Rate vs Actual
Total Expenses Summary
By choosing actual costs over simplified expenses, Tom claims an additional £4,184 in deductions and saves around £1,088 more in tax compared to using simplified rates.