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Most self-employed tradesmen in the UK don’t struggle because they earn too little — they struggle because they don’t set aside enough for tax.
The result?
A £10,000–£20,000 bill in January that catches them off guard.
In this guide, I’ll show you exactly how much tax to set aside, how the system actually works, and how to avoid the most common mistakes.
Before we continue, download the free Tradesman Financial Toolkit. It includes a Tax Set-Aside Calculator, Cash Flow Planner, Day Rate Calculator and more.
Why Tradesmen Get Caught Out by Tax
Many self-employed tradesmen get caught out by tax because the system works very differently from being employed. When you work for a company, tax and National Insurance are automatically deducted through PAYE, so you never really see the money before it goes to the government.
But when you’re self-employed, clients pay you the full amount and it can feel like it’s all yours to spend.
The problem is that a large portion of that money actually belongs to HM Revenue and Customs (HMRC), and if you don’t set it aside throughout the year, the bill can come as a nasty shock.
If you’re not fully clear on how the system works, it’s worth reading How Self-Employed Tax Works for Tradesmen
Many tradesmen also make avoidable mistakes that increase what they owe. I cover these in my guide on The Most Common Tax Mistakes Self-Employed Tradesmen Make.
The Most Common Tax Mistakes Self-Employed Tradesmen Make
Payments on Account (Why Your Tax Bill Feels Like It Doubles)
Another reason tradesmen get caught out is something called payments on account.
Once you’ve completed your first tax return, HMRC may ask you to start paying part of next year’s tax in advance.
That means:
- You’re paying last year’s tax
- AND part of next year’s at the same time
This is one of the main reasons people panic in January — and why planning ahead matters.
If you’ve just received your first unexpected bill, understanding Payments on Account properly can save a lot of stress. Payments on Account Explained for Tradesmen
Also read – How to Avoid the January Tax Panic
Irregular Income Makes It Easy to Overspend
Income in the trades isn’t consistent.
Some months are strong, others are quiet.
The problem is:
Tax is based on your yearly income, not monthly cash flow.
So even if money feels good now, a tax bill could already be building in the background.
Irregular income is one of the biggest reasons tradesmen struggle financially even when work is busy. I explain this more in Why Tradesmen Struggle With Cash Flow.
Why Tradesmen Struggle With Cash Flow
The 30% Rule Most Tradesmen Use
A simple rule used by experienced tradesmen:
Set aside 25–30% of everything you earn
This usually covers:
- Income Tax
- National Insurance
The easiest way to do this is:
- Get paid
- Immediately move 30% into a separate account
- Treat it as untouchable
Example: £50,000 Income
If you earn £50,000:
- Set aside 30% = £15,000
Your actual bill may be lower depending on expenses, but:
✔ You won’t be caught short
✔ Any extra becomes savings
Not sure how much tax you personally should be setting aside?
Try my free Tradesman Tax Set-Aside Calculator to estimate your own numbers in seconds. Read – Tradesmen Tax Set-Aside Calculator
How Tax Actually Works (Simple Breakdown)
When you’re self-employed, you don’t pay tax on everything you earn.
You pay tax on profit.
That means:
Income – Expenses = Profit
This is calculated and submitted each year through your Self Assessment.
If you want a full breakdown of this process, read How Self-Employed Tax Works for Tradesmen
National Insurance Explained Simply
As well as Income Tax, you’ll also pay National Insurance.
This includes:
- A small fixed amount
- A percentage based on your profit
It’s all calculated together in your Self Assessment and paid to HMRC.
Should You Use An Accountant?
Many tradesmen assume an accountant is expensive, but a good accountant often saves far more tax than they cost.
If you’re unsure whether you need one, I break this down in my guide Do Tradesmen Need an Accountant?
Do Tradesmen Need an Accountant
The Biggest Mistake Tradesmen Make
The most common mistake is simple:
Treating all income as if it’s theirs
When you get paid, part of that money already belongs to HMRC.
If you spend it, you’ll feel the pressure later.
A Simple System That Works
Most experienced tradesmen use this:
- Account 1 → All income
- Account 2 → Tax account
Every payment:
- Move 25–30% immediately
No thinking. No stress later.
Using a separate business account makes managing tax far easier. I compare the best options in my guide to the Best Business Bank Accounts for Self-Employed Tradesmen. Best Business Bank Accounts
Expenses: The Part Most Tradesmen Miss
One of the biggest ways to reduce your tax bill is claiming expenses properly.
Common allowable expenses include:
- Tools and equipment
- Fuel and vehicle costs
- Materials
- Insurance
- Accountant fees
- Phone and internet
- Training
If you’re not claiming correctly, you’re overpaying tax.
Keeping accurate records is just as important as claiming expenses correctly. I explain the best systems in Best Expense Tracking Apps for Tradesmen.
Read – Best Expense Tracking Apps and What Expenses Can Tradesmen Claim Against Tax
Example: How Expenses Reduce Tax
Let’s say:
- Income = £60,000
- Expenses = £15,000
Your taxable profit is:
£45,000
That’s what tax is calculated on — not the full £60k.
How Much Tax You’ll Typically Pay
For most tradesmen earning:
£30,000–£60,000 profit
You’ll usually pay around:
20%–30% total (tax + NI)
This is why the 30% rule works.
Quick Tax Saving Guide
| Annual Profit | Suggested Tax Savings |
|---|---|
| £20,000 | £5,000 (25%) |
| £40,000 | £10,000 (25%) |
| £60,000 | £15,000 (25%) |
When 30% Isn’t Enough
If your profit goes above £50,000, your tax rate increases.
In these cases, setting aside closer to 30–35% is safer.
Real Scenario (Where It Goes Wrong)
A tradesman earns £60,000.
Spends most of it.
End of year:
- Tax bill = ~£12,000
- Payments on account added
Total due:
£18,000+
No savings → serious stress.
This is exactly the situation many try to avoid:
How to Avoid the January Tax Panic
The Lesson Most Tradesmen Learn Once
This usually only happens once.
After that, people realise:
The tax money was never theirs
And they start setting it aside properly.
The Simple Rule (Final Takeaway)
If you remember one thing:
Save 25–30% of your income
Track your expenses
Don’t touch your tax money
Do that, and tax stops being stressful.
Frequently Asked Questions
How much tax should self-employed tradesmen save each month?
Most self-employed tradesmen should set aside around 25% to 30% of income to cover tax and National Insurance.
Do self-employed tradesmen pay tax on turnover?
No. Tax is paid on profit after allowable expenses are deducted.
Should tradesmen use a separate account for tax savings?
Yes. Moving tax money into a separate account immediately helps avoid overspending.
What happens if I cannot pay my tax bill?
HMRC may charge interest and penalties. I explain this fully in What Happens If You Don’t Pay Your Tax as a Tradesman?
Read –
What Happens If You Don’t Pay Your Tax as a Tradesman
Conclusion
If you are self-employed in the trades, tax is not something to think about once a year.
It needs managing every single month.
The simplest system is:
- Save 25–30% immediately
- Track every expense properly
- Keep tax money separate
- Plan ahead for payments on account
Most tax problems are not caused by earning too little.
They happen because good tradesmen treat tax money as spendable income.
If you want help managing your finances better, download my Free Tradesman Financial Toolkit and take control of your business properly.
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