CIS Explained: Construction Industry Scheme Guide for Contractors

Why is 30% of your pay disappearing before it even hits your bank account? If you’re a subcontractor who hasn’t registered for CIS, that’s exactly what’s happening — and it doesn’t have to be that way.

The Construction Industry Scheme catches out contractors and subcontractors alike. Miss a monthly return? That’s a penalty. Forget to verify a subcontractor? Another penalty. Get the deduction rate wrong? You guessed it. Whether you’re a main contractor managing a team of subbies or a self-employed tradesperson trying to keep more of what you earn, this guide breaks down everything you need to know about CIS — in plain English, not HMRC-speak.

What is the Construction Industry Scheme (CIS)?

The Construction Industry Scheme is HMRC’s system for collecting tax from subcontractors working in the construction industry. Rather than waiting until Self Assessment to collect tax, HMRC requires contractors to deduct money from payments to subcontractors and pay it directly to HMRC on their behalf.

Think of it as a “pay as you earn” system for the construction sector. The deductions count as advance payments toward the subcontractor’s annual tax and National Insurance bill.

Why Does CIS Exist?

Construction has historically been associated with tax avoidance and cash-in-hand work. CIS was designed to:

Ensure tax is collected at the point payment is made
Reduce the risk of subcontractors disappearing without paying their tax
Create an audit trail of construction industry payments
Improve compliance across the sector

While CIS creates administrative work, it provides structure and helps legitimate businesses operate on a level playing field.

Who is Affected by CIS?

CIS applies to most construction work in the UK, including:

Building work (houses, offices, factories, etc.)
Civil engineering (roads, bridges, tunnels)
Repairs and decorating
Installing heating, lighting, ventilation systems
Ground works and demolition
Scaffolding
Site clearance

Contractors

You’re a contractor under CIS if you:

Pay subcontractors for construction work
Have an average annual expenditure on construction of £3 million or more (including materials) in the last three years, OR
Are a construction business paying subcontractors regardless of expenditure level, OR
Are a business outside construction (like property developers or housing associations) spending £3 million+ annually on construction

Contractors must register for CIS, verify subcontractors before paying them, make deductions, and file monthly CIS returns.

Subcontractors

You’re a subcontractor under CIS if you:

Carry out construction work for a contractor
Are self-employed or run a limited company
Don’t have an employment contract with the contractor

Most tradespeople working for builders, developers, or main contractors are subcontractors under CIS—electricians, plumbers, carpenters, bricklayers, plasterers, roofers, and general builders.

Who is Exempt from CIS?

CIS doesn’t apply to:

Employees with PAYE contracts
Architecture and surveying work (design and planning)
Scaffolding hire (without erection)
Delivery of materials only
Carpet fitting and professional cleaning
Work outside the UK

If you’re unsure whether your work falls under CIS, it’s worth getting professional advice—operating outside CIS when you should be in it can result in significant penalties.

CIS Registration: Contractors and Subcontractors

Both contractors and subcontractors need to register with HMRC, but the processes and benefits differ.

Contractor Registration

Contractors must register for CIS before taking on their first subcontractor. You’ll need:

Your Unique Taxpayer Reference (UTR)
Company registration number (if limited)
National Insurance number (if sole trader)
Business bank details

You can register online through your HMRC business account or by calling HMRC’s CIS helpline. Registration typically takes around 5 working days.

Once registered, you’ll have access to HMRC’s CIS online system for verifying subcontractors and filing monthly returns.

Subcontractor Registration

Subcontractors don’t have to register for CIS, but there’s a significant financial incentive to do so. Here’s why:

Unregistered subcontractors have 30% deducted from their payments (excluding materials).

Registered subcontractors have only 20% deducted.

Gross payment status subcontractors have 0% deducted—they’re paid in full and handle their own tax.

For a subcontractor earning £2,000 per week (excluding materials), that’s the difference between receiving £1,400 (30% deduction) or £1,600 (20% deduction)—an extra £200 per week in cash flow just from registering.

To register as a subcontractor, you need:

Unique Taxpayer Reference (UTR)
National Insurance number
Business bank details
Company information (if limited)

Registration can be done online or by phone and usually processes within 2-3 weeks. Once registered, you’ll receive a Unique Taxpayer Reference that contractors will use to verify you.

Gross Payment Status: The Holy Grail

Gross payment status allows subcontractors to be paid without any CIS deductions. To qualify, you must:

Have been registered for CIS for at least 12 months
Demonstrate good tax compliance (returns filed on time, tax paid)
Pass HMRC’s “business test” (genuine business, not disguised employment)
Show sufficient turnover (£30,000+ for sole traders, £30,000+ per partner for partnerships, £100,000+ for companies)

Gross payment status is reviewed annually and can be removed if you fail to meet compliance standards. However, for established subcontractors with good cash flow management, it’s a significant advantage.

Verification: The Critical First Step

Before making any payment to a subcontractor, contractors must verify them with HMRC. This process determines the correct deduction rate and ensures you’re dealing with legitimate workers.

How to Verify Subcontractors

Verification must be done before the first payment and repeated:

If the subcontractor’s business structure changes (e.g., sole trader becomes a limited company)
If you haven’t paid them in the last 12 months

You’ll need:

The subcontractor’s full name (or company name)
Their Unique Taxpayer Reference (UTR) OR National Insurance number (if individual) OR Company Registration Number (if limited)
Their business address

Verification is done through HMRC’s online CIS system and provides an instant response:

20% deduction – Registered subcontractor
30% deduction – Unregistered subcontractor
0% deduction – Gross payment status
Verification failed – Details don’t match HMRC records

What if Verification Fails?

If verification fails, don’t make payment until you’ve resolved the issue. Common problems include:

Subcontractor provided wrong UTR or business details
Recent business structure changes not yet updated with HMRC
Subcontractor isn’t registered for Self Assessment

Ask the subcontractor to check their details and try again. If it continues to fail, they may need to contact HMRC directly to resolve discrepancies in their records.

Understanding CIS Deduction Rates

The amount deducted depends on the subcontractor’s CIS status and what you’re paying for.

What Gets Deducted?

Deductions apply to labour costs only, not materials. If you pay a subcontractor £5,000 where £1,500 is for materials they’ve purchased, you only make deductions on £3,500.

The subcontractor should provide clear invoices separating labour and materials. If they don’t, you must deduct from the full amount.

Calculating Deductions

Registered subcontractor (20% rate):

Total payment: £3,500 (labour only)
Deduction: £3,500 × 20% = £700
Net payment to subcontractor: £2,800

Unregistered subcontractor (30% rate):

Total payment: £3,500 (labour only)
Deduction: £3,500 × 30% = £1,050
Net payment to subcontractor: £2,450

Gross payment status (0% rate):

Total payment: £3,500
Deduction: £0
Net payment to subcontractor: £3,500

Payment Statements

After making a payment, you must provide the subcontractor with a payment statement showing:

Gross amount paid (before deductions)
Cost of materials (if applicable)
Amount of CIS deduction
Net amount paid
Your CIS contractor reference

These statements are crucial for subcontractors when completing their Self Assessment returns—they use them to claim credit for deductions already made.

Monthly CIS Returns: Your Key Obligation

Contractors must file a CIS return every month, even if you haven’t paid any subcontractors during that period.

What’s Included in CIS Returns?

Each monthly return must detail:

Each subcontractor you’ve paid
Total payments made (gross)
Amount deducted
Cost of materials (if separately identified)

Returns cover tax months running from the 6th of one month to the 5th of the next (e.g., 6 January to 5 February).

Filing Deadlines

CIS returns must be filed by the 19th of the month following the tax month end. For example:

Tax month: 6 January to 5 February
Filing deadline: 19 February
Payment deadline: 22 February (if paying electronically)

Returns can only be filed online through HMRC’s CIS system. There’s no paper option.

Paying CIS Deductions to HMRC

The deductions you’ve made must be paid to HMRC by the 22nd of the month (if paying electronically) or 19th (if paying by post—which nobody does anymore).

If you also operate PAYE, CIS deductions are paid alongside your PAYE liabilities using the same payment reference.

Nil Returns

If you haven’t paid any subcontractors during a tax month, you still must file a “nil return” stating no payments were made. Failure to file nil returns results in penalties just like failing to file returns with payments.

CIS and Reverse Charge VAT

If you’re VAT registered, you need to understand how the domestic reverse charge for construction services interacts with CIS.

Since March 2021, most CIS-covered construction services between VAT-registered contractors and subcontractors fall under the reverse charge. This means:

Subcontractors don’t charge VAT on their invoices
Contractors account for the VAT through their own VAT return
The contractor both claims input VAT and declares output VAT (usually cancelling each other out)

How CIS and Reverse Charge Work Together

Subcontractor invoice:

Labour: £3,500
Materials: £1,500
VAT: £0 (reverse charge applies)
Total invoice: £5,000

Contractor’s obligations:

CIS deduction on £3,500 labour = £700 (if 20% rate)
Pay subcontractor £4,300 (£5,000 - £700)
Account for reverse charge VAT on £5,000 on your VAT return

The reverse charge doesn’t affect the CIS deduction calculation—it only changes how VAT is handled.

When Reverse Charge Doesn’t Apply

The reverse charge has exemptions:

Payments under £250
Subcontractors not VAT registered
Work outside CIS scope
End-users (consumers) paying contractors

Both parties need to understand whether reverse charge applies to avoid VAT compliance errors.

Common CIS Mistakes to Avoid

Even experienced construction businesses make CIS errors that trigger penalties and compliance issues.

Not Verifying Subcontractors Before Payment

Some contractors pay first and verify later—or don’t verify at all. This results in penalties and potential disputes with HMRC about deduction rates.

Solution: Build verification into your payment approval process. Don’t authorize payments until verification is complete.

Incorrect Deduction Calculations

Mistakes include:

Deducting from the full invoice including materials
Using the wrong deduction rate (30% instead of 20%)
Not making deductions for gross payment status subcontractors who’ve lost their status

Solution: Keep accurate records of verification responses and use accounting software that calculates deductions automatically based on subcontractor status.

Missing Monthly Return Deadlines

CIS returns are due monthly without exception. Late filing triggers automatic penalties:

First late return: £100
Second late return in the same tax year: £200
Third and subsequent: £300 each

Solution: Diarize deadlines well in advance. Set reminders a week before each deadline. Consider using accounting software that prompts you when returns are due.

Poor Record Keeping

HMRC can request CIS records going back six years. You must keep:

Verification records for each subcontractor
Payment and deduction records
Copies of monthly returns
Payment statements issued to subcontractors

Solution: Use digital record-keeping systems. Cloud accounting software automatically maintains CIS records and makes them searchable.

Not Providing Payment Statements

Subcontractors need payment statements to complete their tax returns. Failing to provide them causes problems for subcontractors and can damage working relationships.

Solution: Issue payment statements at the same time as making payments. Email or provide printed copies with payment remittances.

Confusing CIS with PAYE

Some contractors mistakenly treat subcontractors as employees or vice versa. CIS is for genuine self-employed subcontractors; employees must be on PAYE.

Solution: Understand employment status tests. If someone works exclusively for you, follows your instructions closely, and you provide tools and equipment, they’re likely an employee regardless of what the contract says.

HMRC Penalties and Compliance

HMRC takes CIS compliance seriously, with penalties for various failures:

Late Filing Penalties

£100 for each late monthly return
Additional daily penalties if returns are more than 2 months late
Tax-geared penalties if returns are more than 6 months late

Failure to Operate CIS Correctly

If HMRC determines you should have made deductions but didn’t:

You’re liable to pay HMRC the deductions you should have made
Penalties up to 100% of the deductions can apply
You may not be able to recover the money from the subcontractor

Incorrect Returns

Penalties for careless or deliberate errors:

Careless errors: Up to 30% of the tax involved
Deliberate errors: Up to 70% of the tax involved
Deliberate and concealed: Up to 100% of the tax involved

Late Payment

Interest charges accrue on CIS deductions paid late, and penalties apply if payment is more than 30 days late.

Getting Professional CIS Help

Let’s be honest — you didn’t get into construction to spend your evenings filing CIS returns. Managing compliance alongside actually running a business is a lot, and many contractors and subcontractors find specialist accounting support pays for itself.

When to Get CIS Accounting Help

Consider professional CIS services if:

You’re registering as a contractor for the first time
You’re managing multiple subcontractors and struggling with monthly returns
You’ve received HMRC penalty notices or compliance queries
You’re unsure about verification processes or deduction calculations
You want to apply for gross payment status as a subcontractor
You’re dealing with reverse charge VAT alongside CIS
You need construction-specific bookkeeping and tax advice

CIS Accounting Services in Worcester and Birmingham

At Severn Accounting, we specialize in construction industry accounting across Worcester, Birmingham, and the wider Midlands. We understand the unique challenges construction businesses face—managing subcontractors, maintaining cash flow, and staying on top of CIS compliance.

Our CIS services include:

Contractor CIS management – Subcontractor verification, monthly return preparation and filing, deduction calculations, payment statement generation
Subcontractor accounting – Self Assessment returns incorporating CIS deductions, gross payment status applications, tax planning
CIS bookkeeping – Construction-specific bookkeeping from £100/month with proper CIS coding and tracking
CIS compliance reviews – Audit your current CIS processes and identify compliance gaps
HMRC representation – Support with HMRC queries, penalty appeals, and compliance investigations
Reverse charge VAT – Navigate the interaction between CIS and VAT reverse charge rules

Our CIS return preparation and filing service starts from just £150 per month, designed specifically for construction contractors who want peace of mind that their CIS obligations are handled correctly and on time.

Whether you’re a main contractor managing a team of subcontractors across multiple sites or a self-employed tradesperson trying to maximize your take-home pay, we can help you navigate CIS rules efficiently.

Get CIS Support Today

CIS doesn’t have to be a headache. The rules are fiddly, but once you’ve got a proper system in place — or someone handling it for you — it just ticks along in the background while you get on with the actual work.

If you’re spending evenings wrestling with monthly returns, or you’ve already had a penalty letter land on the doormat, it’s worth having a conversation with us. We work with construction businesses across Worcester and Birmingham every day, and we know CIS inside out.

Give us a call on 07950 244741 or drop an email to info@severnaccounting.co.uk. We’ll have a chat about your situation — no charge, no obligation.

Worcester Office: 1 Shaw Street, Shaw Mews, Worcester, WR1 3QQ
Birmingham Office: Colmore Row, Birmingham, B3 2BJ

See our construction and CIS accounting services or get in touch to get started. You might also find our guide on filing your self-assessment return useful if you’re a subcontractor sorting out your year-end tax.