Self-Employed Tax Guide 2026/27: Income Tax, NI and Self Assessment

Self-Employed Tax Guide 2026/27

Becoming self-employed means taking full responsibility for your tax through the Self Assessment system. Unlike PAYE employees whose tax is automated, sole traders, freelancers, and partners must calculate, report, and pay their own tax — on a schedule that can surprise first-time filers. This guide covers everything you need to know.

Registering as Self-Employed

Register with HMRC as self-employed as soon as you start trading for profit, and by no later than 5 October following the end of the tax year in which you started (e.g., 5 October 2027 for starting in 2026/27).

Register online at gov.uk/register-for-self-assessment. You receive a Unique Taxpayer Reference (UTR) — keep this safe.

What Tax Does a Sole Trader Pay?

Three main obligations:

Self-Employed Tax and NI 2026/27

Calculating Taxable Profit

Taxable profit = Revenue − Allowable Expenses. Expenses must be incurred "wholly and exclusively" for the business.

Allowable — most commonly used:

Not allowable:

• Personal drawings or living expenses
• Client entertainment (not permitted for sole traders)
• Capital expenditure (use capital allowances separately)
• Normal clothing (only protective/uniform qualifies)

Worked Example: Freelance Designer, £48,000 Revenue

Effective rate on revenue: 18.2%. Effective rate on profit: 20.5%.

The Self Assessment Calendar

Payments on Account — The Big Surprise

If your total tax and NI bill exceeds £1,000, HMRC requires advance payments towards next year's liability: two payments of 50% each.

First year filing example:

• Year 1 tax bill: £8,749
• By 31 January: pay £8,749 (Year 1) + £4,375 (first payment on account for Year 2)
• By 31 July: pay £4,375 (second payment on account for Year 2)
• Total cash outflow by July: £17,499

Budget for approximately 150% of your expected first-year bill to avoid a cash crisis.

Key Ways to Reduce Self-Employed Tax

1. Pension Contributions Every pound contributed to a pension (SIPP) reduces both income tax AND Class 4 NI. On a £5,000 contribution at 29% combined rate: saves £1,450. The pension also receives £1,250 basic rate top-up. Net cost of £5,000 pension: only £3,550.

2. Trading Allowance Under £1,000 from self-employment: completely tax-free. No need to register or file below this threshold.

3. Use of Home as Office The flat rate (£6/week) is simple but the actual cost calculation often yields more for those with significant household bills.

4. Mileage Rate vs Actual Vehicle Costs For lower-value vehicles, the 45p/mile rate typically exceeds actual costs. For newer expensive vehicles, actual costs may be higher.

5. Carry Back Losses A bad year generating a loss can be carried back against the previous year's profits — potentially generating a tax refund.

Class 2 NI: Why You Should Pay It

Class 2 voluntary contributions cost just £3.45/week (£179.40/year) but earn you a qualifying NI year towards the State Pension. Each qualifying year adds ~£6.71/week (£349/year) to your eventual State Pension.

Paying Class 2: costs £179/year. Return: £349/year State Pension increase. Payback: ~6 months of retirement.

Unless you already have 35 qualifying years, always pay voluntary Class 2.

Frequently Asked Questions

Q: Do I need to register for VAT? Only if your taxable turnover exceeds £90,000 in a rolling 12-month period. Below this, registration is optional. Voluntary registration can be beneficial if you sell to VAT-registered businesses and incur significant business expenses.

Q: Can I deduct the cost of a car? Not fully in year 1 (unless electric, which may qualify for 100% AIA). Cars use writing down allowances: 18% reducing balance for low-emission vehicles, 6% for higher emission. The simplified mileage rate (45p/mile) avoids this complexity and is usually better for lower-value vehicles.

Q: I had a loss this year — what are my options? Three options: (1) offset against other income in the same year; (2) carry back one year and claim a refund; (3) carry forward against future profits. Option 1 or 2 can generate immediate cash.

Q: I want to incorporate — what are the tax implications? Transferring business assets to a limited company can trigger capital gains tax on goodwill. Incorporation Relief may defer the gain. Always take professional advice before incorporating an established business.