Enter your net profit (income after business expenses) and see your full tax bill — UK income tax plus Class 4 National Insurance, or US self-employment tax plus federal income tax.
Your business
£
Take-home after tax
—
from — profit
Take-home –Income tax –NI–
Income tax
–
National Insurance
–
Total tax
–
Effective rate
–
Self-employed tax at a glance — 2025/26
UK sole trader: income tax on profit above £12,570 (20% / 40% / 45%) plus Class 4 NI at 6% (£12,570–£50,270) and 2% above.
US self-employed: 15.3% self-employment tax (12.4% Social Security + 2.9% Medicare) on 92.35% of net earnings, plus federal income tax.
Self-employment / NI is additional to income tax, not part of it.
US: half of self-employment tax is deductible against income tax.
A freelancer's profit after expenses is £50,000. They pay income tax plus Class 4 NI.
Income tax (£37,430 @ 20%)£7,486
Class 4 NI (£37,430 @ 6%)£2,246
Total tax£9,732
🇺🇸
US self-employed, $80,000 profit
A US contractor nets $80,000. Self-employment tax comes first, then income tax on what's left after the deductions.
Self-employment tax$11,304
Federal income tax$7,971
Total tax$19,275
How self-employed tax works
Self-employed people are taxed on profit — what's left after deducting allowable business expenses from turnover — not on everything they invoice. On top of income tax, you also pay a social-security contribution: Class 4 National Insurance in the UK, or self-employment tax (Social Security + Medicare) in the US. That second layer is what makes self-employment more expensive than it first looks.
The US twist: 92.35% and the half-deduction
US self-employment tax is charged on 92.35% of net earnings (a nod to the employer-equivalent portion), and you can deduct half of it when working out income tax — both of which this calculator applies.
Set money aside
Because nothing is withheld at source, self-employed people usually owe a lump sum at filing. A common rule of thumb is to set aside 25–30% of profit, but your effective rate above is the precise figure to budget around.
Income tax on profit above the £12,570 allowance (20/40/45%) plus Class 4 NI at 6% on £12,570–£50,270 and 2% above.
What is the US self-employment tax rate?
15.3% (12.4% Social Security up to the wage base + 2.9% Medicare) on 92.35% of net earnings. Half is deductible against income tax.
Is it on top of income tax?
Yes — it's separate from and additional to income tax. The calculator shows and sums both.
Should I be a sole trader or a limited company?
It depends on profit level, how much you draw, and admin appetite. Compare this with the Corporation Tax and Dividend Tax calculators, and get advice for your situation.
Estimate only. UK figures use 2025/26 income tax + Class 4 NI for a sole trader (Class 2 treated as not payable above the threshold); excludes student loans, payments on account and the High Income Child Benefit Charge. US figures use 2025 single-filer federal income tax + self-employment tax with the standard deduction; excludes state taxes, QBI deduction and credits. Verify with HMRC / the IRS and an accountant. Not tax advice.