What Is a CIS Number

What Is a CIS Number?

If you work in the UK construction industry, either as a subcontractor or contractor, you may have come across the term CIS number. Although not an official label used by HMRC, many people use this term to describe the key tax reference used under the Construction Industry Scheme (CIS).

So, what is a CIS number really? In this guide, we explain what people mean when they refer to a CIS number, how to get one, and why it matters for getting paid correctly under the scheme.

What Does “CIS Number” Actually Mean?

A CIS number typically refers to your Unique Taxpayer Reference (UTR), which is a 10-digit number issued by HMRC when you register for Self Assessment or set up a limited company.

This UTR is the key reference HMRC uses to track your status and payments under the Construction Industry Scheme. When contractors verify subcontractors with HMRC, they use this number along with your name and National Insurance or company registration number to confirm your CIS registration and determine your tax deduction rate.

Although there is no specific document or ID card titled “CIS number,” your UTR functions as your official CIS reference.

Why Is a CIS Number Important?

Your CIS number (UTR) is essential for the following reasons:

• It identifies you when registering for CIS

• Contractors use it to verify your tax status with HMRC

• It determines whether you have tax deducted at 20 per cent or 30 per cent

• It allows HMRC to credit any CIS deductions against your annual tax bill

• It is required when claiming tax refunds or applying for gross payment status

Without a UTR and CIS registration, contractors will deduct tax at the higher 30 per cent rate, which can put pressure on your cash flow.

Who Needs a CIS Number?

You need a CIS number if you are:

• A self-employed subcontractor working in the construction industry

• A limited company acting as a subcontractor or contractor

• A partnership carrying out construction work

• A contractor who pays subcontractors for construction-related services

Anyone working in building, demolition, repairs, electrical, plumbing, decorating, groundwork or similar trades should be registered under CIS if they receive or make payments in a subcontracting arrangement.

How to Get a CIS Number (UTR)

If you are a sole trader or individual subcontractor:

1. Register for Self Assessment with HMRC online at gov.uk

2. HMRC will post your UTR to your home address

3. Once you receive it, register for CIS as a subcontractor using your UTR via your Government Gateway account or by calling 0300 200 3210

If you run a limited company:

1. Register your company with Companies House and HMRC

2. HMRC will send your company a Corporation Tax UTR

3. Use this UTR to register your company for CIS via your Business Tax Account

If you are both a subcontractor and contractor, you must register for both roles separately.

What to Do Once You Have a CIS Number

Once you’re registered and have your UTR:

• Give your UTR to contractors who pay you for construction work

• They will verify you with HMRC, which determines the correct deduction rate

• You should start receiving monthly deduction statements showing how much tax has been deducted

• Keep these records safe for your Self Assessment or Corporation Tax return

Your UTR (CIS number) is also used if you apply for gross payment status, allowing you to receive payments without any deductions.

How to Check Your CIS Number

You can find your UTR (CIS number) on:

• HMRC letters about Self Assessment or Corporation Tax

• Your Government Gateway account

• Previous tax returns

• Letters confirming CIS registration

If you have lost it, call HMRC’s CIS helpline on 0300 200 3210 to request a reminder. You may need to confirm your identity.

Final Thoughts

A CIS number is not a separate or official ID, but rather a common term used to refer to your Unique Taxpayer Reference (UTR) within the Construction Industry Scheme. It is the key reference used by HMRC and contractors to manage your tax and payment status.

Whether you're a self-employed builder, a limited company contractor or a partnership working in construction, having a valid UTR and registering under CIS is essential for getting paid correctly and managing your tax efficiently.