CIS Supply Chain Red Flags: How to Stay Paid and Stay Out of Trouble

For many subcontractors, the Construction Industry Scheme (CIS) is simply part of getting paid. Contractors deduct tax at source, payments arrive slightly reduced, and the paperwork appears relatively straightforward.

But beneath that simple surface sits a supply chain that HMRC watches very closely.

Over the past few years, HMRC has increased enforcement across construction. Investigations often focus on fraud, labour supply chains, false subcontracting arrangements, and unpaid tax further up the chain.

That means even legitimate subcontractors can sometimes find themselves caught up in problems caused by others.

Understanding the warning signs can help you protect your income, avoid payment disputes, and stay clear of HMRC trouble.

Why CIS Supply Chains Matter More Than You Think

Construction projects rarely involve just one contractor and one subcontractor.

Most projects include multiple layers of labour supply. For example:

Developer → Main contractor → Subcontractor → Labour-only subcontractor → Individual workers

Every step in that chain introduces risk.

If someone in the chain fails to meet their tax obligations, HMRC may investigate the structure and the parties involved. In serious cases this can lead to:

• • delayed payments
• • withheld CIS deductions
• • contract disputes
• • HMRC enquiries

Being aware of how these arrangements work is essential for protecting your business.

Red Flag 1: The Contractor Won’t Verify You

Under CIS rules, contractors must verify subcontractors with HMRC before making payments.

Verification determines whether tax should be deducted at:

• • 20% (standard rate)
• • 30% (unverified subcontractor)
• • 0% (gross payment status)

If a contractor refuses to verify you or avoids discussing CIS status, that’s a warning sign.

It could mean:

• • they are not properly registered for CIS
• • they are trying to avoid deductions
• • they are operating outside HMRC rules

Legitimate contractors complete verification as a routine step.

Red Flag 2: Unclear Payment Arrangements

A common problem in construction supply chains is uncertain payment responsibility.

Some subcontractors find themselves in situations where:

• • payment is delayed because the contractor has not been paid
• • invoices move through several intermediaries
• • nobody clearly owns the payment obligation

If the payment structure feels vague or constantly changes, it increases the risk of late or missing payments.

Clear contracts and direct relationships with the contractor help reduce this risk.

Red Flag 3: Requests to Work “Outside CIS”

Occasionally subcontractors are asked to work in ways that avoid CIS deductions entirely.

This may include:

• • being paid as “labour only” without proper documentation
• • receiving payment through unrelated companies
• • being asked to invoice through someone else

These arrangements can create serious problems.

If HMRC later determines that CIS should have applied, the parties involved may face penalties or tax recovery actions.

Working within CIS rules protects both parties and keeps records clear.

Red Flag 4: Missing Payment Statements

Contractors must provide CIS deduction statements showing:

• • the gross amount of the payment
• • the amount deducted
• • the contractor’s details

These statements are essential because they allow subcontractors to claim the deducted tax when completing their Self Assessment return.

If a contractor regularly fails to provide statements, it creates uncertainty about what has been reported to HMRC.

Without proper records, reconciling your tax position becomes much harder.

Red Flag 5: The Supply Chain Is Too Complicated

Another warning sign is an unusually complex chain of subcontractors and agencies.

When labour passes through several companies before reaching the site, it can create:

• • confusion about responsibilities
• • unclear payment flows
• • increased risk of fraud

HMRC has investigated numerous construction supply chains where workers were several layers removed from the main contractor.

Keeping relationships simple and transparent reduces exposure to these risks.

How to Protect Yourself as a Subcontractor

While you cannot control the behaviour of every company in a construction project, there are practical steps that help protect your position.

Verify who you are working for

Make sure you understand:

• • who the contractor is
• • who will be paying you
• • how CIS deductions will be handled

Keep clear records

Maintain records of:

• • invoices
• • CIS deduction statements
• • payment confirmations

These documents are essential when preparing tax returns and resolving disputes.

Check your CIS deductions regularly

You should periodically confirm that deductions reported by contractors match the payments you receive.

This ensures that your tax record with HMRC is accurate.

Why CIS Compliance Is Becoming More Important

Construction remains one of the sectors HMRC monitors most closely.

The government sees the scheme as a key tool for reducing tax evasion and improving transparency in labour supply chains.

As enforcement increases, subcontractors who keep proper records and work with compliant contractors are far less likely to encounter problems.

Understanding CIS supply chain risks isn’t just about avoiding HMRC issues. It also helps ensure that the work you complete actually results in reliable payment.

Summary

The Construction Industry Scheme is designed to make tax collection simpler in construction, but complex labour supply chains can introduce risks.

Subcontractors should watch for warning signs such as:

• • contractors avoiding CIS verification
• • unclear payment structures
• • requests to bypass CIS rules
• • missing deduction statements
• • overly complicated supply chains

Recognising these red flags early can help protect your income and keep your business operating within HMRC rules.