Self-Employed Tax Calculator

Work out your 2026/27 Income Tax and Class 4 National Insurance on a sole-trader profit, how much to set aside each month, and the first-year payments-on-account demand.

Read the full Self-Employed Tax guide

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Your figures

Annual profit (after expenses)£30,000

Your self-employment income minus expenses.

PAYE salary (optional)£0

If you also have a job, your profit is taxed in the bands above your salary.

Tax region

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Tax and National Insurance due

£4,532

Income Tax

£3,486

Class 4 NI

£1,046

Profit after tax

£25,468

Effective rate 15.1% on profit; marginal rate 26% on the next pound.

Breakdown

Income Tax	£3,486
Class 4 National Insurance	£1,046
Total to pay	£4,532
Profit after tax	£25,468

Class 2 NI: Treated as paid (profit is above the £7,105 small profits threshold), so nothing extra to pay.

Set aside each month

£378

About 15% of your profit. Move it to a separate pot the day you are paid, before you can spend it.

Your first January bill: £6,798

Because your bill is over £1,000, the first 31 January demands the full £4,532 plus a £2,266 payment on account towards next year - about 150% of one year's tax. A second £2,266 is then due by 31 July.

How this is worked out

Income Tax: your profit (stacked on top of any PAYE salary) is taxed at 20% above the £12,570 Personal Allowance, 40% above £50,270 and 45% above £125,140.
Class 4 NI: 6% on profits between £12,570 and £50,270, then 2% above. Class 2 is treated as paid automatically once profit passes the £7,105 small profits threshold.
Set-aside: the total tax and NI divided by 12, so you can move it to a separate pot each month.
Payments on account: if your bill is £1,000 or more, HMRC adds a 50% advance toward next year each January and July, so the first January is about 150% of one year's tax.

Frequently asked questions

How much tax do I pay on a self-employed profit of GBP 45,000?

On GBP 45,000 of profit in 2026/27 you pay GBP 6,486 Income Tax plus GBP 1,945.80 Class 4 National Insurance, a total of GBP 8,431.80, or about 18.7% of profit. The first GBP 12,570 is covered by the Personal Allowance.

What is the real marginal tax rate for the self-employed?

In the basic-rate band it is 26%, not 20%: 20% Income Tax plus 6% Class 4 National Insurance on the same pound of profit. Above GBP 50,270 the combined marginal rate is 42% (40% Income Tax plus 2% Class 4).

How much should I set aside for tax?

A safe rule is to move your effective rate of profit into a separate pot as you are paid - roughly 20-25% for a basic-rate sole trader, more once profits pass GBP 50,270. This calculator shows the exact monthly figure for your profit.

Why is my first tax bill so much bigger than I expected?

If your bill is GBP 1,000 or more, your first 31 January payment includes the full year plus a 50% payment on account towards next year, with another 50% due that 31 July. The first profitable year therefore demands about 150% of one year of tax at once.

Does this include Class 2 National Insurance?

Class 2 is treated as paid automatically once your profit is above the GBP 7,105 small profits threshold, so there is nothing extra to pay. Below that threshold you can pay it voluntarily at GBP 3.65 a week to protect your State Pension record.