How Self-Employed Tax Works for Tradesmen in the UK (Complete Guide)

Understanding tax when you’re self-employed can feel confusing, especially if you’ve spent most of your career working under PAYE.

Many tradesmen get their first tax bill and are shocked by how much they owe, simply because nobody explained how the system works.

In this guide, we’ll break down how self-employed tax works in the UK, including Income Tax, National Insurance, expenses, and why some tax bills seem to double.

If you’re already self-employed and unsure how much to save, you should also read How Much Tax Should Tradesmen Set Aside

Why Tax Is Different When You’re Self-Employed

When you work as an employee, tax is handled automatically through PAYE. Your employer deducts Income Tax and National Insurance before you get paid.

When you’re self-employed, you receive the full amount and are responsible for paying tax yourself.

This is done through a Self Assessment tax return submitted to HM Revenue and Customs (HMRC).

Your tax is based on your profit, not your total income.

Profit = Income – Expenses

If you don’t understand this properly, it’s easy to get caught out — especially in your first year.

That’s why many tradesmen underestimate their tax bill and struggle later.
How Much Tax Should Tradesmen Set Aside

Registering as Self-Employed

If you start working for yourself, you need to register with HMRC.

When You Need to Register

You must register if you earn over £1,000 in a tax year (Trading Allowance).

Even side work counts.

How to Register

You’ll need to:

• Create a Government Gateway account
• Register for Self Assessment
• Declare yourself as a sole trader

HMRC will then send you a Unique Taxpayer Reference (UTR).

What Happens After You Register

You become responsible for:

• Tracking income
• Recording expenses
• Submitting a tax return
• Paying your own tax

This is where most people start to feel overwhelmed — but it becomes simple once you understand the system.

Income Tax Explained (Simple)

Income Tax in the UK works in bands.

• £0–£12,570 → 0%
• £12,571–£50,270 → 20%
• £50,271+ → higher rates

You only pay higher rates on the portion above each band.

Example:

If you earn £35,000 profit, you only pay tax on the amount above £12,570.

National Insurance for Tradesmen

Self-employed workers also pay National Insurance.

This includes:

• Class 2 (small fixed amount)
• Class 4 (percentage of profit)

These are calculated and paid alongside your Income Tax through your Self Assessment.

Allowable Expenses (Where You Save Money)

One of the biggest advantages of being self-employed is claiming expenses.

This reduces your taxable profit — meaning you pay less tax.

Common examples:

• Tools
• Fuel
• Materials
• Insurance
• Accountant fees
• Phone use

Most tradesmen under-claim simply because they don’t track properly.

For a full breakdown, read:
What Expenses Can Tradesmen Claim Against Tax

Payments on Account (Why Your Tax Bill Feels Bigger)

This is where most people get caught out.

If your tax bill is over £1,000, HMRC may ask you to pay part of next year’s tax in advance.

So you pay:

• This year’s tax
• PLUS part of next year

Example:

Tax bill = £3,000

You may pay:

• £3,000 (last year)
• £1,500 (advance payment)

Total = £4,500

This is why people panic — it feels like the bill has doubled.

How to Avoid the January Tax Panic

When Tax Is Due

There are two key dates:

31 January

• Submit tax return
• Pay full bill
• Pay first payment on account

31 July

• Pay second payment on account

Missing these leads to penalties.

How Much Tax Should Tradesmen Save?

A simple rule:

Save 25–30% of your profit

This usually covers:

• Income Tax
• National Insurance

Saving consistently avoids stress.

For a full breakdown with examples:
How Much Tax Should Tradesmen Set Aside

A Simple System That Works

Most experienced tradesmen use this:

1. Separate tax account

Move 25–30% every time you’re paid

2. Track expenses weekly

Stops you missing deductions

3. Stay consistent

Removes stress completely

This is simple but very effective.

Example (Putting It All Together)

A self-employed electrician earns:

• £60,000 income
• £20,000 expenses

Profit = £40,000

Tax and National Insurance are calculated on that £40,000 — not the full £60k.

Final Thoughts

Self-employed tax isn’t complicated — but it is different.

Most problems come from:

• Not understanding profit vs income
• Not setting money aside
• Not planning for payments on account

Once you understand these, tax becomes routine instead of stressful.