How to Get a CIS Number

At Towerstone Accountants we provide specialist CIS accountancy services for contractors and construction businesses across the UK. We created this webpage for subcontractors and contractors who want clear guidance on the Construction Industry Scheme, including registration, deductions, refunds, and ongoing reporting obligations. Our aim is to help you stay compliant with HMRC, avoid costly errors, and understand how CIS affects your tax position.

When someone asks me how to get a CIS number, what they are usually really asking is how to make sure they are paid properly for construction work without unnecessary deductions or problems with HMRC. I see this question come up constantly with new subcontractors, people switching from cash jobs to legitimate contracts, and even experienced trades who suddenly find 30 percent being taken off their invoices with very little explanation. From my experience running my own accountancy firm and working closely with construction clients, I can say with confidence that getting a CIS number is one of the most important early steps you can take if you work in construction.

In this article I am going to explain exactly what a CIS number is, who needs one, how to get it, and what happens once you have it. I will also cover the common misunderstandings I see, why some people think they have a CIS number when they do not, and how to avoid the costly mistakes that often arise from poor advice or guesswork. My aim is to give you a clear, practical understanding so you can deal with contractors confidently and stay on the right side of HMRC.

By the end of this guide, you should understand how to get a CIS number, what information you need, how long it takes, and how it fits into your wider tax responsibilities.

What a CIS Number Actually Is

One of the first things I always clarify is that a CIS number is not a separate standalone reference in the way many people imagine. There is no single card or certificate called a CIS number that HMRC posts out, despite what you may hear on sites or from other trades.

When people refer to a CIS number, they are usually talking about confirmation that they are registered under the Construction Industry Scheme and can be verified by contractors. In practice, this means your tax details are recognised by HMRC’s CIS system and linked to your Unique Taxpayer Reference and National Insurance number or company details.

Once you are registered, contractors can verify you with HMRC and apply the correct deduction rate. That verification confirmation is what most people think of as their CIS number.

Understanding this distinction is important because it avoids the frustration of waiting for something that does not technically exist in the way people expect.

Why You Need a CIS Number

If you carry out construction work and are paid by contractors, having CIS registration in place is essential. Without it, contractors are legally required to deduct tax at a higher rate from your payments.

In real terms, this usually means the difference between 20 percent being deducted or 30 percent being deducted from your labour payments. That extra 10 percent can seriously affect cash flow, especially for sole traders who rely on regular income to cover materials, fuel, tools, and living costs.

Beyond the immediate financial impact, being properly registered also signals professionalism. Contractors expect legitimate subcontractors to be CIS registered, and in my experience, those who are not often struggle to secure better quality or longer term work.

Who Needs to Get a CIS Number

CIS applies to most people and businesses working in construction, not just traditional builders. I often see confusion here, particularly among newer trades.

You will usually need CIS registration if you are a subcontractor doing construction work for a contractor. This applies whether you are a sole trader, part of a partnership, or operating through a limited company.

It also applies to contractors who pay subcontractors for construction work, even if construction is not their main business activity. I regularly deal with property developers, landlords, and companies that only occasionally commission building work but still fall within CIS.

Construction work for CIS purposes includes a wide range of activities, such as building, alterations, repairs, extensions, demolition, groundwork, and certain types of installation. It is broader than many people realise, and this is where people often get caught out.

When You Should Get a CIS Number

Timing is critical, and this is one area where early action makes a real difference.

If you are starting out as a subcontractor, you should apply for CIS registration as soon as you know you will be carrying out construction work. Ideally, this should be done before you submit your first invoice or receive your first payment.

If you delay, contractors have no choice but to apply the higher 30 percent deduction. While that tax can usually be reclaimed later through your tax return, the short term cash flow impact can be painful.

In my experience, many people only realise they need a CIS number after seeing a much smaller payment than expected hit their bank account. At that point, the damage is already done.

What You Need Before You Apply

Getting a CIS number is straightforward if you are prepared. HMRC does not ask for anything unusual, but the details must be accurate and consistent with their records.

Before applying, you should have the following information available:.

• Your full legal name as registered with HMRC

• Your National Insurance number

• Your Unique Taxpayer Reference if you are self employed

• Your company UTR and registration number if you operate a limited company

• Your business address and contact details

• The date you started trading or expect to start

One issue I see regularly is people applying before registering as self employed. CIS registration does not replace self employment registration, both are required. If you have not registered as self employed, that must be done first.

Registering as Self Employed First

For sole traders, this step is crucial and often missed.

Before you can get a CIS number, you must be registered as self employed with HMRC. This creates your Self Assessment record and issues your Unique Taxpayer Reference.

Without this, HMRC cannot properly register you under CIS, and contractors will not be able to verify you correctly.

Registering as self employed is usually done online and can take a few days for your UTR to be issued. I always advise clients to do this as early as possible, even if they are only just starting out.

How to Get a CIS Number as a Sole Trader

Once you are registered as self employed, you can apply for CIS registration.

This is usually done online through your Government Gateway account. If you do not have one, you will need to set this up first, which typically takes only a short amount of time.

During the application, HMRC will ask for your personal and business details and confirm the type of construction work you carry out. They will then link your self employment record to the CIS system.

Once approved, contractors will be able to verify you and apply the standard 20 percent deduction rather than the higher unregistered rate.

How to Get a CIS Number for a Limited Company

If you operate through a limited company, the process is slightly different but still manageable.

The company must be registered with HMRC for Corporation Tax, and a company UTR must be in place. The CIS registration then links to the company rather than you personally.

Limited companies can register as subcontractors, contractors, or both, depending on the nature of their work.

I often see confusion where directors assume their personal CIS registration covers the company. It does not. Companies must be registered separately, even if the director is already CIS registered as an individual.

Verification and Confirmation

Once you have applied, HMRC will process your registration and confirm your CIS status. There is no physical CIS number issued, but your details will be live on the CIS system.

Contractors verify you using your name, National Insurance number, and UTR or company details. Once verified, they receive confirmation of the deduction rate to apply.

This verification confirmation is what most people refer to when they talk about a CIS number.

Understanding CIS Deduction Rates

It is worth spending time understanding how deduction rates work, because this affects how much money you actually receive.

There are three rates under CIS:.

• 20 percent for registered subcontractors

• 30 percent for unregistered subcontractors

• 0 percent for those approved for gross payment status

Most people start on the 20 percent rate. This deduction is applied only to the labour element of your invoice, not materials, provided the invoice is correctly structured.

The tax deducted is not lost. It is credited against your Income Tax and National Insurance when your tax return is completed.

Gross Payment Status and CIS Numbers

Some people believe getting a CIS number automatically means no tax is deducted. This is not correct.

Gross payment status is a separate approval and comes with strict conditions around turnover, compliance history, and timely tax filings.

In my experience, it is something to aim for once your business is established and you have a track record of meeting your obligations. It is not something most new subcontractors qualify for immediately.

What Happens After You Get Registered

Once you are registered and verified, CIS becomes part of your ongoing tax position.

As a subcontractor, you should receive monthly deduction statements from contractors showing the tax deducted. These should be kept safely, as they are needed when preparing your tax return.

As a contractor, you take on monthly reporting responsibilities, including submitting CIS returns and paying deductions to HMRC.

This is where good bookkeeping and professional support make a real difference.

Common Problems I See with CIS Numbers

Over the years, certain issues come up repeatedly.

People think they are registered when they are not
Self employment registration is missed
Details do not match HMRC records
Limited companies are not registered separately
Verification is not completed before payment

Most of these problems are avoidable with proper advice at the start.

How CIS Affects Your Tax Return

CIS deductions are taken into account when your tax return is prepared.

For sole traders, deductions are offset against Income Tax and National Insurance. If too much tax has been deducted, you may be due a refund.

For limited companies, deductions can be offset against PAYE liabilities or reclaimed through the company’s accounts.

This is why accurate records and correct CIS registration are so important.

Final Thoughts

Getting a CIS number is not complicated, but it is essential if you work in construction. In my experience, most problems arise not because the system is difficult, but because it is misunderstood or ignored until it causes financial pain.

If you register early, make sure your details are correct, and understand how CIS fits into your wider tax position, it becomes a routine part of doing business rather than a constant worry.

If you are unsure whether you need CIS registration, or you want reassurance that everything is set up correctly, getting proper advice early can save you a significant amount of time, money, and stress over the long term.

You may also find our guidance on what is a cis number and how to check your cis status helpful when dealing with related CIS questions. For a broader overview of CIS rules, compliance, and support, you can visit our CIS guidance hub.