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Side hustle tax calculator 2026–27

Estimate the Income Tax and National Insurance on your side hustle for the 2026–27 tax year (6 April 2026 to 5 April 2027), and how much to put aside each month. It uses the rates for England, Wales and Northern Ireland; Scotland has different Income Tax bands.

It runs in your browser. Nothing you type is stored or sent anywhere, and there’s no sign-up.

Everything you expect to take this tax year, before costs.

Stock, materials, fees, phone share and so on. If you enter business miles below, leave out fuel, insurance and repairs.

Claimed at the flat rate: 55p a mile for the first 10,000, then 25p.

Your yearly salary or pension taxed through PAYE, before tax. Leave blank if the side hustle is your only income.

Your estimate for 2026–27

Enter your side hustle income to see the Income Tax and National Insurance you might owe, and how much to put aside each month.

This is an estimate only, not tax advice. It assumes your figures are for the whole tax year and doesn’t cover everything that can change a real bill — check GOV.UK or an accountant for your own situation.

How the estimate works

Your taxable profit is your side hustle income minus either your costs or the £1,000 trading allowance. Costs are your expenses plus the flat mileage allowance on any business miles. The calculator uses your costs once they come to more than £1,000, and the allowance otherwise, because HMRC lets you claim one or the other.

Income Tax is worked out on your profit stacked on top of any salary or pension, so your job uses your Personal Allowance first and your profit is taxed at the rate your total income reaches. Class 4 National Insurance is worked out on your profit alone. The monthly figure is the total divided by 12. Read more in PAYE job plus side hustle and National Insurance on side hustle income.

The rates and the maths are the same ones the Hamster app uses, copied from its tax settings for 2026–27. They were last checked against GOV.UK on 25 October 2026. How we check our numbers.

Personal Allowance
£12,570, reduced by £1 for every £2 of income over £100,000
Income Tax
20% up to £50,270, 40% up to £125,140, 45% above
Class 4 National Insurance
6% on profit from £12,570 to £50,270, 2% above
Trading allowance
£1,000
Mileage (cars and vans)
55p a mile for the first 10,000, then 25p

What it leaves out

  • Scottish Income Tax rates
  • Student loan repayments, which Self Assessment collects on side hustle income too
  • Voluntary Class 2 National Insurance
  • Other income such as savings interest, dividends, rental income or capital gains
  • Tax already deducted from your salary that differs from a standard tax code
  • Losses from earlier years and capital allowances

Want this worked out as you go?

The free Hamster app for Android does the same sum every time you log a sale, a shift or a cost, and shows it next to what you’ve already put aside. Get Hamster on Google Play.