UK self-employed individuals pay income tax (20–45%) plus Class 4 National Insurance (6% on profits £12,570–£50,270; 2% above) and Class 2 NI (£3.45/week if profits exceed £12,570). At £50,000 profit: income tax ~£7,540, Class 4 NI ~£2,268, Class 2 NI ~£179 = total ~£9,987 (20% effective). Payments are split: 31 January (50% on account) and 31 July (50% on account), with balancing payment the following January.
At a glance
Key Facts
Income Tax (Basic Rate)
20% on profits £12,570–£50,270
Income Tax (Higher Rate)
40% on profits £50,271–£125,140
Income Tax (Additional Rate)
45% above £125,140
Class 4 NI
6% on profits £12,570–£50,270; 2% above
Class 2 NI
£3.45/week (2026) if profits above £12,570
Payment Dates
31 January and 31 July (on account); 31 January following year (balance)
Official Authority
HM Revenue & Customs (HMRC)
Introduction
UK self-assessment catches many freelancers, self-employed professionals, and landlords off-guard — not because the calculations are particularly complex, but because of the payments on account system. In your first year of self-employment, you can face paying 150% of one year's tax bill in a single January, covering both the previous year's balancing payment and 50% of the current year's advance.
This guide explains how UK self-assessment income tax and National Insurance are calculated for self-employed individuals in 2026, what expenses are deductible, how the payments on account system works, and how to avoid the 5% late payment penalty on underpaid balancing payments.
Section 01
Income Tax on Self-Employed Profits
According to HM Revenue & Customs (HMRC), self-employed individuals pay income tax on net trading profit — revenue minus allowable expenses — at the same rates as employees:
Taxable Profit
Rate
£0–£12,570 (personal allowance)
0%
£12,571–£50,270
20% (basic rate)
£50,271–£125,140
40% (higher rate)
Above £125,140
45% (additional rate)
The personal allowance (£12,570) phases out between £100,000 and £125,140 — losing £1 for every £2 of income above £100,000. This creates the infamous 60% effective marginal rate in that band, which applies equally to self-employed as to employees.
Trading Allowance
Self-employed individuals with very low trading income (under £1,000 of gross receipts) can claim the £1,000 trading allowance instead of filing full accounts. Above £1,000, actual expenses must be tracked and deducted.
Section 02
National Insurance for Self-Employed 2026
Self-employed individuals pay two classes of National Insurance — fundamentally different from employees who pay Class 1:
Class 2 NI — Fixed Weekly Amount
Class 2 NI is a flat weekly contribution: £3.45 per week in 2026, payable if annual profits exceed £12,570. Annual cost: £3.45 × 52 = £179.40/year. It is collected via self-assessment, not a separate payment. Class 2 NI counts toward your State Pension entitlement and is one of the cheapest ways to build NI qualifying years.
Class 4 NI — Profit-Based
Class 4 NI is calculated on profits at:
6% on profits between £12,570 and £50,270
2% on profits above £50,270
Total NI at Different Profit Levels
Annual Profit
Class 2 NI
Class 4 NI
Total NI
£20,000
£179
£447
£626
£35,000
£179
£1,347
£1,526
£50,270
£179
£2,262
£2,441
£80,000
£179
£2,862
£3,041
£100,000
£179
£3,262
£3,441
Section 03
Total Tax at Key Profit Levels
The table below combines income tax and NI for 2026, assuming single taxpayer, full personal allowance, standard trading activity only:
Annual Profit
Income Tax
NI (Cl.2+4)
Total Tax
Net Take-Home
Effective Rate
£20,000
£1,486
£626
£2,112
£17,888
10.6%
£35,000
£4,486
£1,526
£6,012
£28,988
17.2%
£50,000
£7,486
£2,421
£9,907
£40,093
19.8%
£70,000
£15,432
£2,862
£18,294
£51,706
26.1%
£100,000
£27,432
£3,441
£30,873
£69,127
30.9%
£150,000
~£55,432
£3,841
~£59,273
~£90,727
~39.5%
Note: The £100,000–£125,140 band where the personal allowance phases out creates significantly higher marginal rates. At £120,000, the marginal rate on each additional pound is 60% (40% income tax + tapering allowance effect).
Section 04
Payments on Account: The System That Surprises New Self-Employed
HMRC does not wait until 31 January to collect all your tax. Self-employed individuals with a tax liability above £1,000 must make payments on account — advance payments towards the following year's tax bill:
Payment Schedule
31 January in the tax year: First payment on account = 50% of previous year's tax bill
31 July following the tax year end: Second payment on account = 50% of previous year's tax bill
31 January following year: Balancing payment = final tax minus payments on account already made
The First Year Problem
In your first year of self-employment, you have no history — so no payments on account were made. At 31 January in year 2, you must pay:
The entire previous year's tax bill (balancing payment)
PLUS the first payment on account for the current year (50% of year 1 bill)
On a £50,000 profit year 1: tax bill = ~£9,907. At the first January deadline you owe approximately £14,860 (£9,907 + 50%). Budget carefully from your first day of self-employment.
Reducing Payments on Account
If you expect lower profits in the current year vs the previous year, you can apply to HMRC to reduce your payment on account. If you over-reduce and your actual bill is higher, HMRC charges interest on the shortfall — but no penalty if you applied in good faith.
Section 05
Allowable Expenses for Self-Employed
Deducting allowable expenses is the primary tool for reducing your self-assessment tax bill. HMRC allows 'wholly and exclusively for business' expenses:
Travel: mileage at 45p/mile (first 10,000 miles), 25p/mile thereafter; public transport; flights for business trips
Professional fees: accountant, solicitor, trade body memberships
Marketing: website costs, advertising, business cards
Training: courses directly related to your current trade or profession
Business insurance: professional indemnity, public liability
Bank charges: business account fees
Home Office (Simplified Method)
HMRC allows a flat-rate home working allowance without the need to apportion actual costs:
25–50 hours/month: £10/month
51–100 hours/month: £18/month
101+ hours/month: £26/month
Alternatively, claim actual costs apportioned by floor space or time. The actual method can produce larger deductions but requires careful records.
Capital Allowances
Equipment purchases (laptop, camera, tools) are deducted via capital allowances rather than directly as expenses. The Annual Investment Allowance (AIA) of £1,000,000 means almost all equipment purchases can be fully deducted in the year of purchase via 100% first-year allowance.
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How much National Insurance do self-employed people pay in the UK in 2026?
Self-employed pay Class 2 NI (£3.45/week = £179/year if profits exceed £12,570) plus Class 4 NI (6% on profits £12,570–£50,270, 2% above). At £50,000 profit: Class 2 £179 + Class 4 £2,262 = £2,441 total NI. This is significantly less than employed workers who pay Class 1 NI at 8% up to £50,270.
Q
What are the self-assessment payment on account dates?
Payments on account are due 31 January (in the tax year) and 31 July (following the tax year end). Each is 50% of the previous year's tax bill. The balancing payment (actual tax minus payments on account) is due 31 January the following year. In the first year of self-employment, there are no payments on account — but you'll pay the full first-year bill plus the first payment on account simultaneously at the first January deadline.
Q
Can I reduce my payments on account if my income drops?
Yes. Log into HMRC's online Self Assessment account and apply to reduce your payment on account if you expect lower profits this year. Be careful: if you under-estimate and your actual bill is higher than the reduced payment, HMRC charges interest on the shortfall (currently 7.25% per annum). There's no penalty for a good-faith reduction, only interest on the shortfall amount.
Q
What expenses can I deduct as a self-employed person?
Allowable expenses include: office costs (stationery, software, equipment via capital allowances), professional fees (accountant, insurance), business travel (mileage at 45p/mile), marketing, training directly related to your current work, and home office costs (either actual proportional costs or HMRC's simplified flat rate of £10–£26/month). Expenses must be 'wholly and exclusively' for business. Dual-purpose expenses (e.g., a business dinner with a personal friend) are not deductible.
Q
Do I need to register for VAT as a self-employed person?
VAT registration is mandatory if your taxable turnover exceeds £90,000 in any rolling 12-month period. Below £90,000, registration is voluntary. Voluntarily registering can be beneficial if you have significant VAT-bearing input costs to reclaim, or if your clients are VAT-registered businesses who can reclaim the VAT you charge. For B2C businesses (selling to individuals), voluntary VAT registration increases prices unless you absorb the 20% cost.
Q
What is the 60% marginal rate for self-employed at £100,000?
Between £100,000 and £125,140, every £2 of additional income costs you £1 of personal allowance. This means you pay 40% income tax on the income, plus 40% income tax on the lost allowance = 60% effective marginal rate. Self-employed (and employees) in this band should consider pension contributions, which directly reduce income and can restore the personal allowance. At £100,000, a pension contribution of £12,540 restores the full allowance and saves approximately £7,524 in tax.
Q
Do US citizens in the UK still have to file US taxes?
Yes. US citizens file annual US federal returns regardless of UK residency. The UK-US tax treaty and Foreign Tax Credit (FTC) typically cover US liability for income taxed in the UK, since UK rates generally exceed US rates at higher incomes. However, UK Class 4 NI is not always FTC-creditable. Self-employed US citizens in the UK should consult a specialist experienced with both HMRC and IRS obligations.
Disclaimer:This guide provides general information and illustrative calculations about UK self-assessment taxation for educational purposes only. Tax rates and thresholds change annually. Always verify current figures with HMRC or a qualified UK tax adviser (accountant or tax agent). This is not tax advice.