When do I need to register for self-assessment?

You must register with HMRC by 5 October following the end of the tax year in which you became self-employed. For example, if you started self-employment in June 2025, register by 5 October 2026.

What happens if I miss the self-assessment deadline?

HMRC charges an automatic £100 penalty for filing late, even if you owe no tax. After 3 months, daily penalties of £10 per day (up to 90 days) apply. After 6 and 12 months, further penalties are charged.

Can I do my own self-assessment?

Yes. Many tradespeople file their own returns using HMRC online services. However, if your affairs are complex (e.g. CIS, multiple income sources, VAT), an accountant can save you time and potentially money.

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Self-Assessment Tax for UK Tradespeople: What You Need to Know

21 February 20261 min read

Self-assessment basics for tradespeople

If you are self-employed — whether as a plumber, electrician, builder, or any other trade — you need to file a self-assessment tax return each year. This guide covers the key things you need to know.

Key deadlines

5 April — end of the tax year
31 October — deadline for paper tax returns
31 January — deadline for online tax returns AND payment of tax owed
31 July — second payment on account (if applicable)

How much tax will you owe?

Your tax bill depends on your profit (income minus allowable expenses). Use our self-assessment calculator to get an estimate.

For 2025/26, the income tax bands are:

Personal allowance: £12,570 (no tax)
Basic rate: 20% on £12,571 to £50,270
Higher rate: 40% on £50,271 to £125,140
Additional rate: 45% on income over £125,140

National Insurance contributions

Self-employed tradespeople pay two types of NIC:

Class 2: £3.45 per week (if profits exceed £12,570)
Class 4: 6% on profits between £12,570 and £50,270, plus 2% on profits above £50,270

Allowable expenses

You can deduct legitimate business expenses from your income before calculating tax:

Tools, equipment, and safety gear
Van/vehicle costs (fuel, insurance, servicing)
Materials you buy for jobs
Public liability insurance
Phone and broadband (business proportion)
Accountant fees
Software subscriptions (e.g. InvoiceAdept)
Protective clothing and workwear

Keeping good records

HMRC requires you to keep records of all income and expenses for at least 5 years. Digital records are now essential — especially with Making Tax Digital requirements coming in from April 2026.

InvoiceAdept automatically tracks every invoice you send and every expense you record, keeping your records digital and export-ready.

Estimate your tax bill

Use our free self-assessment calculator to estimate your income tax and NIC for the current tax year. Then try InvoiceAdept free to keep your records organised all year round.

Ready to get started?

InvoiceAdept helps UK tradespeople send invoices, track payments, and stay compliant — all from one place.