CIS Contractor Responsibilities : What You Must Do Before Paying Subcontractors (2026)

CIS affects whether subcontractors can be paid, what percentage you must deduct, and what you need to submit each month. Most payment delays and CIS headaches come from two things:

• subcontractors not being verified properly
• contractors not running CIS correctly month to month

This guide explains CIS from the contractor side, and focuses on what you need to do to stay compliant and keep payments moving.

What CIS is trying to achieve (and why verification exists)

CIS was created because construction has always been a high-risk sector for tax under-reporting. Payments move quickly, work is often subcontracted, and there have been long-running issues with people getting paid but not declaring the income properly.

Over time, HMRC has also had to deal with fraud chains, where networks set up layers of subcontractors to make payments hard to trace, and tax is not paid correctly.

That is why CIS works the way it does. Contractors must:

• verify who they are paying
• apply the correct deduction rate
• report and pay deductions regularly

Verification is not just a formality. It is the control that keeps the scheme working.

Are you a contractor under CIS?

You are usually treated as a CIS contractor if your business pays subcontractors for construction work.

That includes businesses that are not “builders” in the traditional sense. If you pay trades for construction work as part of your operations, you can still fall under CIS rules.

Many small companies become contractors under CIS without realising it until they try to pay someone and get asked for verification.

If you need to register as a CIS contractor and get it set up correctly from the start:

What contractors must do before paying a subcontractor

Before you pay a subcontractor, you need to follow a proper CIS process. If you skip steps, the risk sits with you as the contractor.

Step 1: Confirm the subcontractor’s details

You need the subcontractor’s correct information so they can be verified. In most cases this includes:

• legal name (or business name)
• UTR (Unique Taxpayer Reference)
• National Insurance number (for individuals) or company registration details (for limited companies)

If the subcontractor gives incorrect details, verification can fail, and that can delay payment.

Step 2: Verify the subcontractor

Verification tells you what deduction rate to apply. This is where the subcontractor is put into the right category for CIS deductions.

Contractors normally see one of these outcomes:

• 0% if the subcontractor has Gross Payment Status
• 20% if the subcontractor is registered
• 30% if the subcontractor is not registered

This matters for cashflow and for trust. Subcontractors notice immediately if the wrong percentage is taken.

If you want to avoid verification problems and payment delays, set up your CIS correctly early.

The most common CIS verification problems (and how to avoid them)

Most CIS problems are simple, but painful in real life.

1) The subcontractor is not registered

If they are not registered, they may fall into the 30% deduction rate, even if they insist they “normally pay 20%”.

Many subcontractors only realise they are not registered when their first payment comes in short.

2) The subcontractor gives the wrong information

This happens a lot, especially with:

• trading names vs legal names
• sole traders using an old UTR
• new limited companies where details do not match

A single wrong digit can cause verification to fail.

3) The contractor rushes payment without verifying

Some contractors pay first and plan to fix it later. That is when CIS becomes messy.

If you want smooth operations, verify before the first payment and keep it consistent.

If you are about to pay subcontractors and want the CIS side done properly:

What contractors must do every month under CIS

Once you are registered as a contractor, you have ongoing responsibilities. This is where many small construction businesses get caught out.

1) Track who you paid and what work they did

You need clean records of:

• which subcontractors you paid
• the amounts paid for labour
• the CIS deductions taken
• payment dates

This is not about fancy paperwork. It is about being able to report correctly and avoid disputes later.

2) Submit your CIS return

Contractors must submit regular CIS returns that declare payments and deductions.

If you miss returns, it can create penalties and ongoing compliance issues. It can also impact your ability to manage subcontractors smoothly, because problems tend to stack up.

3) Pay CIS deductions to HMRC

The deductions you take from subcontractors are not “yours to hold”. They must be passed on properly.

This is one reason CIS causes stress for new contractors. It changes your cashflow and forces discipline in record-keeping.

4) Keep consistent deduction rates

Your subcontractors will expect consistency. If you suddenly deduct 30% from someone who is usually on 20%, you will get calls immediately.

A clean verification process reduces disputes and keeps relationships intact.

If you are new to contractor CIS returns and want to avoid mistakes, a registration service can help you get the setup right.

What if you are both contractor and subcontractor?

This is very common in construction.

Example:

• you do work for larger contractors (so you are a subcontractor)
• you hire labour or other trades for your own jobs (so you are a contractor)

In that case, you may need CIS registration that covers both roles.

If you only register as subcontractor, you can still end up stuck when you start paying others and need contractor verification and reporting.

If you need to register as both contractor and subcontractor, do it in one go and avoid rework later.

Quick checklist for contractors paying subcontractors

Before making your first CIS payment, make sure you can answer “yes” to these:

• Am I registered as a CIS contractor?
• Do I have the subcontractor’s correct legal details?
• Have I verified them and confirmed the deduction rate?
• Am I recording labour and deductions properly?
• Do I know what I need to submit each month?

If you get these right early, CIS stops being stressful. It becomes a routine process that keeps your payments clean and predictable.