All depends on your profit.
You pay Income Tax and National Insurance
You have a personal allowance from the government which entitles you to make a profit in 2020-21 of £12500 before you pay any tax.
Anything over £12500 and you pay 20% Tax (and between £50,001-£150,000 then 40%)
CLASS 2: If you have taxable income in 2020-21 of over £6240 then you have to pay Class 2 at £3.05 per wk. but only on the weeks you have worked.
CLASS 4: If you have taxable income in 2020-21 of between £9500-£50,000 then the difference is charged at 9%