If you are asking “do you pay 40% tax on CIS?”, the short answer is no — not as a standard CIS deduction rate.
For most UK subcontractors working under the Construction Industry Scheme (CIS), contractors deduct 20% from labour payments if you are registered with HMRC, or 30% if you are not registered. There is no normal 40% CIS deduction rate.
That said, some subcontractors get confused because they may still end up paying higher-rate income tax overall depending on their total earnings for the tax year. That is different from the CIS deduction taken from your invoice payments.
So if you have been searching “do subcontractors pay 40% tax?”, this guide explains exactly what is deducted, what you may actually owe, and how to stay on top of CIS paperwork on live projects.
CIS tax rates: 20% or 30%, not 40%
Under CIS, the deduction is usually made by the contractor before they pay the subcontractor. The contractor sends that deduction to HMRC on the subcontractor’s behalf.
In practice, the standard CIS deduction rates are:
- 20% if the subcontractor is registered for CIS
- 30% if the subcontractor is not registered for CIS
- 0% if the subcontractor has gross payment status
This is where the confusion often starts on site. A bricklayer, dryliner or groundworks gang may look at a remittance advice and see a substantial deduction, then assume they are being taxed at an unusually high rate. But under CIS itself, 40% is not the normal rate.
Why people think CIS is 40%
There are a few common reasons subcontractors believe they are paying 40% tax under CIS.
1. They are mixing up CIS deductions with income tax bands
CIS deductions are advance payments towards your tax and National Insurance bill. They are not always your final tax position.
For example, a subcontractor may have CIS deducted at 20%, but if their total annual profit pushes them into the higher-rate tax band, they could end up paying more tax when they complete their Self Assessment tax return. That can make it feel like they are “on 40% tax”, but that is income tax law, not a 40% CIS rate.
2. They are not registered for CIS
If you are not properly registered, a contractor can deduct 30%. On a busy site, that extra 10% hit can feel severe, especially if materials have already been paid for and cash flow is tight.
A roofing subcontractor invoicing £5,000 for labour could see:
- £1,000 deducted at 20% if registered
- £1,500 deducted at 30% if not registered
That difference matters when you are trying to pay labourers, fuel, plant hire or scaffold costs.
3. Other deductions or accounting issues are being included
Sometimes subcontractors confuse CIS with:
- income tax due through Self Assessment
- Class 2 and Class 4 National Insurance
- accountant adjustments
- old tax debts collected by HMRC
- incorrect contractor deductions
When several deductions stack up, the total can feel far higher than expected.
Do subcontractors pay 40% tax?
The accurate answer is:
- No, subcontractors do not usually pay 40% tax under CIS deductions
- Yes, some subcontractors may pay 40% income tax on part of their profits if their earnings are high enough
That distinction is important.
CIS is simply a method of deducting money at source in the construction industry. It applies to many trades including:
- bricklayers
- electricians
- plumbers
- carpenters
- groundworkers
- plasterers
- demolition subcontractors
- civils gangs
The contractor deducts CIS from the labour element of the invoice, not from materials if those materials are clearly shown and allowable.
A practical site example
Imagine a subcontractor on a housing development in Manchester submits an invoice for:
- Labour: £4,000
- Materials: £1,200
- Total invoice: £5,200
If they are registered for CIS, the contractor usually calculates CIS on the labour only:
- 20% of £4,000 = £800 CIS deduction
So the subcontractor receives:
- £5,200 total invoice
- minus £800 CIS
- £4,400 paid
That is not 40% tax. It is a 20% CIS deduction on the labour portion.
Now imagine the subcontractor is not registered:
- 30% of £4,000 = £1,200 CIS deduction
They receive:
- £5,200 total invoice
- minus £1,200 CIS
- £4,000 paid
Again, still not 40%.
When higher-rate tax can still apply
Where people get caught out is at year end.
If your profits are high enough, some of your income may fall into the higher-rate tax band. In that case, your CIS deductions may not fully cover your final tax bill.
For example, a successful subcontractor working across several commercial fit-out jobs may have CIS deducted at 20% all year. But after allowable expenses are worked out, they may still owe additional tax through Self Assessment if their taxable income is above the relevant threshold.
So the key point is this:
CIS deductions and your final tax liability are not always the same thing.
How to avoid paying the wrong CIS rate
If you want to avoid unnecessary deductions and cash flow headaches, there are a few practical steps.
Register for CIS properly
If you are not registered, contractors can deduct 30%. Registering correctly helps ensure you are on the standard 20% rate, unless you qualify for gross payment status.
Make sure invoices separate labour and materials
CIS is usually deducted from labour, not allowable materials. If your invoices are unclear, you could end up with a bigger deduction than necessary.
On real sites, this often happens when rushed applications for payment do not clearly break out:
- labour
- materials
- plant
- variations
- retention
Check monthly CIS statements
Contractors should provide a statement showing what they deducted. Always check it against your application, invoice and payment notice.
A wrong deduction repeated across several projects can become a serious issue by year end.
Keep accurate records
Good record keeping makes a big difference when reconciling CIS deductions, chasing missing statements, or preparing your tax return.
This is where digital site admin tools help.
Using SiteSamurai to stay on top of CIS admin
CIS problems are often not caused by the tax rules themselves. They are caused by poor paperwork, missing backup, unclear invoices and weak communication between site, office and accounts.
With SiteSamurai, construction teams can tighten up the admin that supports accurate CIS handling by:
- keeping job records organised in one place
- tracking site activity and completed work clearly
- improving supporting evidence for applications and invoices
- reducing disputes over labour, progress and variations
- making it easier to match what was done on site against what was billed
For example, if a subcontractor is working on a refurbishment package and the contractor questions the labour value claimed, having a clear digital record of site activity, progress updates and completed items can help resolve the issue quickly. That means fewer payment disputes and less risk of CIS deductions being applied incorrectly because the paperwork is vague.
In short, SiteSamurai helps subcontractors and contractors run cleaner, better-documented jobs, which is exactly what you need when money, deductions and HMRC reporting are involved.
Common CIS mistakes subcontractors should avoid
Here are some of the most common issues seen across UK construction projects:
- assuming CIS is a final tax bill
- thinking there is a standard 40% CIS rate
- failing to register for CIS
- not separating materials on invoices
- not checking deduction statements
- losing records for expenses and deductions
- leaving tax calculations until the last minute
These mistakes can hurt cash flow, especially for small subcontractors juggling multiple sites and tight payment cycles.
Final answer: do you pay 40% tax on CIS?
No — you do not normally pay 40% tax under CIS.
The usual CIS deduction rates are:
- 20% if registered
- 30% if not registered
- 0% with gross payment status
If you end up paying tax at 40%, that would usually relate to your overall income tax position, not because CIS itself deducts 40% from your payments.
If you are a subcontractor, the best move is to:
- register correctly
- keep clean invoices and records
- check all CIS statements
- use a system like SiteSamurai to keep project admin accurate and organised
That way, you reduce payment disputes, improve cash flow visibility and avoid nasty surprises when your tax return is due.