Free tools
Tax maths,done for you.
Free calculators and checkers for UK Self Assessment. No sign-up, no email. Just the numbers.
All tools
Self-employed tax calculator
Income tax, Class 4 National Insurance and payments on account from your profit.
£4,531.80
on £30,000 profit
Do I need to file?
Nine yes-or-no questions to see whether you need a 2025/26 tax return.
9
quick questions
Payments on account calculator
Whether HMRC wants advance payments, how much, and when they're due.
31 Jan · 31 Jul
two instalments
Late penalty calculator
Late filing and late payment penalties, plus interest, month by month.
£100+
from day one
Full tax calculator
Self Assessment, CIS, multiple incomes and salary after tax in one place.
4-in-1
calculators
All tools give illustrative estimates using 2025/26 rates for England, Wales and Northern Ireland.
Your tax return isn't going to do itself.
Actually, TaxGo gets pretty close.