If you work in UK construction as a subcontractor, CIS registration is one of the first things you need to sort out — and one of the most expensive things to ignore.

The Construction Industry Scheme requires contractors to deduct tax from subcontractor payments before paying them. How much they deduct depends entirely on your registration status. Registered? 20%. Not registered? 30%. That's an extra £100 lost on every £1,000 of labour — money that sits with HMRC until you file your Self Assessment and reclaim it.

Registration is free. It takes about ten minutes online. And yet thousands of subcontractors work without it, either because they didn't know they needed to, or because they assumed their UTR was enough. It isn't.

The Three CIS Deduction Rates — and What They Cost You

Before we get into how to register, it's worth understanding exactly what's at stake. CIS has three deduction rates, and your registration status determines which one applies to you:

The difference between registered and unregistered on a £3,000 invoice is £300. Over a year of steady work, that can easily add up to £3,000–£5,000 sitting with HMRC instead of in your bank account. You'll get it back eventually — but "eventually" doesn't pay for fuel, tools, or rent this month.

What You Need Before You Start

Before you can register for CIS, you need two things:

Don't Have a UTR Yet?

If you've never registered for Self Assessment, you need to do that first. You can register online at gov.uk. HMRC will send your UTR by post — allow up to 10 working days. Once you have it, you can register for CIS immediately.

How to Register as a CIS Subcontractor — Sole Trader

This is the most common route. If you're a sole trader working as a subcontractor in construction, here's the process:

1. Log in to your HMRC online account using your Government Gateway credentials.
2. Go to the Self Assessment section.
3. During registration, select "working as a subcontractor" — HMRC will automatically register you for CIS.
4. Provide your UTR, National Insurance number, full name, and business address.
5. HMRC processes the registration — typically within a few working days.
6. Give your contractor your UTR and NI number so they can verify you before making payments.

That's it. Once your contractor verifies you through HMRC's system, they'll deduct 20% instead of 30% from your payments going forward.

How Your Contractor Verifies You (And What Happens Next)

Completing your CIS registration with HMRC is only step one. Before a contractor can pay you at the 20% rate (or 0% for gross payment status), they must perform an active verification check through HMRC's online system.

Here is how the verification process works in practice:

• Provide accurate details: Give your contractor your UTR, National Insurance number (or Company Registration Number), and official trading name. These details must match HMRC's records exactly — even a minor typo causes a mismatch error.
• HMRC Verification Check: The contractor logs into HMRC's CIS online service and inputs your details to verify your status.
• Verification Number: Once verified, HMRC issues a unique Verification Number to the contractor. If you are registered, the number starts with the letter 'V'. If you are not registered, HMRC assigns a unique reference code instructing the contractor to deduct 30%.
• Confirmation Statement: Your contractor must provide you with a monthly CIS Statement of Pay and Deductions showing the amount paid and tax deducted. Save all these statements — you will need them to claim your refund during Self Assessment.

How to Register a Limited Company for CIS

Limited companies register differently. You'll use HMRC form CIS305, available online through your Government Gateway account.

You'll need:

• Company UTR (10-digit number)
• Companies House registration number
• National Insurance numbers for each director
• Company bank account details
• Business address (must match Companies House records)

Log in to Government Gateway, navigate to the Construction Industry Scheme section, and complete form CIS305. You can register as a subcontractor only, or apply for gross payment status at the same time.

Online registration typically takes a few working days. If you can't register online, download the postal form CIS305 from gov.uk, complete it, and post it to HMRC at the address on the form. Postal registration can take several weeks.

How to Register a Partnership for CIS

Partnerships use form CIS304. Each partner needs their own UTR, and you'll need the partnership UTR and trading name. HMRC registers the partnership separately from any individual sole trader registrations — even if you're already registered individually, the partnership needs its own CIS registration.

Which Form Do You Need?

Online is always faster. Use postal forms only if you can't access Government Gateway.

Registering as a Contractor

If you pay subcontractors for construction work, you must register as a CIS contractor with HMRC before making your first payment. This applies even if you're primarily a subcontractor yourself — if you subcontract any work to someone else, you're a contractor under CIS for that transaction.

Contractor registration can be done online via your HMRC business tax account or by calling the CIS helpline on 0300 200 3210 (Monday to Friday, 8am to 6pm). You'll need your UTR and employer reference number. Once registered, you must verify every subcontractor with HMRC before paying them and submit monthly CIS returns.

Gross Payment Status: Getting Paid in Full

Once you're registered as a CIS subcontractor at 20%, there's a next level: gross payment status (GPS). This means 0% deduction — you receive the full invoice amount and settle your tax through Self Assessment.

For a subcontractor with £50,000 annual turnover, the difference between 20% and 0% is £10,000 in cash flow throughout the year. That's significant working capital.

To qualify, you must pass three HMRC tests:

After Registration: What Happens Next

Once you're CIS-registered, there are a few things to keep in mind:

• Give every contractor your UTR and NI number — they verify you with HMRC before paying
• Use the same name and address you registered with — mismatches cause verification failures
• You register once — it covers all your CIS work, regardless of how many contractors you work for
• Keep your CIS payment and deduction statements — you'll need them for your Self Assessment
• If you change business structure (sole trader to limited company), you need to register again under the new entity

Your CIS Registration Checklist

• Check if you already have a UTR from a previous Self Assessment registration
• If not, register for Self Assessment at gov.uk — UTR arrives by post within 10 days
• Set up a Government Gateway account (if you don't have one)
• Register for CIS online — select "working as a subcontractor"
• Confirm registration is active — ask your contractor to verify you
• Save your CIS registration confirmation screenshot / email
• Give your UTR and NI number to every contractor you work for
• Consider applying for gross payment status once you meet the £30,000 turnover threshold