CIS Registration Number: A Complete Expert Guide for UK Contractors and Subcontractors

In UK tax practice, few things cause more day-to-day confusion for workers in the construction industry than the question, “How do I get my CIS Registration Number?” or “Why is HMRC not recognising my details under CIS?”
Having supported contractors and subcontractors for over two decades, I’ve seen how a missing or incorrect CIS registration can delay payments, trigger unnecessary deductions, or even result in HMRC compliance letters. The rules themselves are not complex—but CIS processes are unforgiving if you get the details wrong at the start.

This guide explains, in a human and experience-based way, what a CIS Registration Number actually is, how HMRC identifies you under the Construction Industry Scheme, and how to avoid the practical pitfalls that cost workers real money every tax year.

Understanding What “CIS Registration Number” Really Means

One of the most common misconceptions I deal with is the idea that HMRC issues a special, unique “CIS registration number.” In reality, there is no separate CIS number. What HMRC uses depends on your trading status:

If you are a sole trader

HMRC recognises you under CIS using:

• Your Unique Taxpayer Reference (UTR)
• Your National Insurance number (NINO)
• Your legal name and address

Your UTR is effectively what workers mean when they ask for their “CIS Registration Number,” because that is the number used to verify you for 20% deductions instead of the punitive 30%.

If your business is a Limited Company

HMRC identifies your company within CIS using:

• The company UTR
• The company name
• The Company Registration Number (CRN)
• The PAYE reference if the company also runs payroll

Again, there is no separate “CIS number”—your UTR is the core identifier.

If you are a partnership

HMRC uses:

• The partnership UTR
• Each partner’s personal UTR and NI number

Many partnerships mistakenly submit only their personal UTR, which always leads to failed CIS verification.

Why the UTR Matters So Much in CIS

The UTR is HMRC’s backbone for the Construction Industry Scheme. When a contractor verifies a subcontractor, what they’re actually doing is checking the UTR and NI (or UTR + company details). This determines your deduction rate.

Here’s how HMRC responds to a verification request:

This is why workers regularly panic when told they are being deducted 30%—it means their UTR or details are not matched on HMRC’s CIS system.

How to Register and Get Recognised Under CIS (Correct Method)

HMRC allows CIS registration through several routes, and the correct method depends entirely on your business type. Using the wrong one is responsible for most verification failures I see in practice.

Sole traders: How to register for CIS

You must already be registered for Self-Assessment before you can register for CIS. If you’re not yet in Self-Assessment, HMRC will automatically register you when you sign up for CIS.

Register using HMRC’s online service here:
https://www.gov.uk/what-you-must-do-as-a-cis-subcontractor/register-for-the-construction-industry-scheme

You’ll need:

• NI number
• UTR (or HMRC will issue one)
• Address
• Type of construction work you perform

Typical timeframe:
HMRC issues your UTR within 10–14 days if you don’t already have one.

Limited companies: How to register for CIS

This is where many new contractors hit problems.

You must register the company, not yourself.

Use HMRC’s CIS registration portal:
https://www.gov.uk/what-you-must-do-as-a-cis-contractor/register-as-a-contractor-and-subcontractor

Information required:

• Company UTR
• Corporation Tax status
• PAYE reference (if you run payroll)
• Company registration details

Many directors mistakenly give contractors their personal UTR, which always results in 30% deductions.

Partnerships

A partnership must register using the partnership UTR, not partners’ personal UTRs.

HMRC will also record:

• Each partner’s personal UTR
• NI numbers
• Address details

Partnerships are one of the most problematic groups because they assume that “anyone’s UTR will do” when starting out. In reality, mismatched partnership registrations lead to failed verifications for months.

How Contractors Verify Subcontractors Under CIS

Once you provide your UTR to a contractor, they must verify you using HMRC’s CIS portal or accounting software.

The system checks:

• UTR
• NI (for sole traders)
• Company name and CRN (for limited companies)

If your details match HMRC records, you get 20% or 0% deductions. If not, the system defaults to 30%, and often workers blame the contractor—but the issue is nearly always incorrect HMRC records or failure to complete registration.

In practice, I see three common causes of failed verification:

1. The subcontractor recently moved address

HMRC still holds the old address.
CIS will not match.

2. HMRC hasn’t fully processed the CIS registration

This can take 2–4 weeks during busy seasons.

3. The wrong UTR is being used

Very common with:

• Employees turning self-employed
• Directors using personal UTR instead of company UTR
• Partnerships mixing personal and business UTRs

Real-World Example: Sole Trader CIS Verification

A sole trader bricklayer called Jason registers for CIS but forgets to update his address with HMRC. When a contractor tries to verify him:

HMRC returns:
“Unknown – 30% deduction”

Jason loses:

• £600 from a £2,000 job
  instead of
• £400 (if 20% applied)

After he calls HMRC and updates his address, the contractor re-verifies him successfully at 20%.

This is the day-to-day reality of CIS compliance in the UK—small details make big financial differences.

How to Find Your CIS Registration Number (UTR)

If you’ve lost your UTR, HMRC provides it in several places. Over many years, I’ve guided countless workers through recovering their UTR before major jobs or deadlines.

Where your UTR can be found

• SA250 “Welcome to Self-Assessment” letter
• Any previous Self-Assessment tax return (SA100)
• Your Personal Tax Account
• The HMRC App
• Any correspondence from HMRC about Self-Assessment

If you can’t find it, request your UTR here:
https://www.gov.uk/find-lost-utr-number

HMRC will only send it by post to your registered address.

Typical timeframe:
7–10 days.

UTR for limited companies

The company UTR is issued by HMRC shortly after incorporation, usually:

• In the post within 10 days
• Appearing on the company’s Corporation Tax letters

If lost, you can request a replacement through the business tax account.

Gross Payment Status (GPS): The 0% CIS Deduction Option

Some businesses are eligible for 0% CIS deduction if they meet HMRC’s Gross Payment Status criteria. This is ideal for subcontractors who want to improve cash flow.

To qualify, HMRC assesses:

• Your tax compliance history
• Turnover thresholds
• Whether your business is run commercially and properly

Turnover test for Gross Payment Status:

GPS is not permanent—HMRC carries out checks and can withdraw it if filings or payments fall behind.

Table: Overview of CIS Identification Requirements

Common Myths About the CIS Registration Number

Over the years, I’ve seen widespread misunderstandings about CIS numbers, often spread by agencies, labour managers, or inexperienced accountants. Here are the most frequent ones:

“HMRC will email my CIS number.”

Incorrect—HMRC only sends UTRs by post.

“I can start work and give the contractor any number.”

Incorrect. If the UTR doesn’t match HMRC records, you’ll be put on 30% deductions.

“A CIS card will be sent to me.”

This ended decades ago. CIS is entirely digital now.

“The contractor made a mistake with my deductions.”

Contractors have no control over deduction rates; HMRC decides when they verify your UTR.

CIS Registration Number: Full Expert Guide for UK Contractors & Subcontractors

Part 1 laid the groundwork by clarifying that there is no separate HMRC-issued “CIS Registration Number”, and that CIS identity is built around the UTR—personal, company, or partnership.
Now we move deeper into the practical, often messy realities that taxpayers face after registering for CIS, including verification issues, deduction disputes, practical workflows, filing obligations, and how to ensure your records match HMRC’s system.

This second section continues in the same practitioner-led tone: what actually happens after CIS registration, what often goes wrong, and how to correct it efficiently without jeopardising cash flow or triggering compliance checks.

What Happens After You Register for CIS (Worker’s Perspective)

When a sole trader or company finishes CIS registration, HMRC updates your status on the Construction Industry Scheme system. But workers often assume this is instant; it is not.

Typical HMRC processing times:

• Standard CIS registration: 7–20 days
• During April/May (Self-Assessment busy season): 3–6 weeks
• During periods of strike/processing backlog: potentially longer

While HMRC processes your registration, contractors attempting to verify you may receive:

• “Unknown – 30% deduction required”
• “Details do not match”

This is why experienced accountants always recommend:

• Registering with HMRC before you accept your first subcontractor job
• Ensuring your address and identity match exactly what HMRC holds

Even minor inconsistencies (middle names, missing flat numbers, and shortened company names) can force 30% deductions.

How to speed up HMRC recognition

Although HMRC cannot “fast track” CIS registrations, you can:

• Call HMRC CIS Helpline to confirm your registration is complete
• Update your address or personal details if mismatched
• Ask HMRC to “refresh” your record if contractors still receive errors

I’ve had cases where a quick call resolved 30% deduction issues within 48 hours simply because HMRC corrected an outdated address.

Post-Verification: What Contractors See and Must Do

Once a subcontractor is verified, the contractor receives:

• The deduction rate (0%, 20%, or 30%)
• A CIS Verification Number (this is NOT the subcontractor’s number)

Important clarification:

Some subcontractors confuse this verification number with a “CIS Registration Number.”

These are two different things:

Contractors must keep CIS verification numbers for at least 3 years in case of a compliance review.

CIS Monthly Returns: What Happens After Deduction

Once deductions start, contractors must report them every month using a CIS Monthly Return. This is essential because it creates the official record HMRC uses for subcontractors’ tax credit.

Key points:

• Deadline: 19th of every month
• Penalties:
  • £100 immediately after the deadline
  • Increasing up to £3,000 for longer delays

If a contractor fails to file, subcontractors may later struggle to claim their CIS refund because HMRC will have no record of deducted tax.

Common real-world scenario

A subcontractor finishes the tax year and submits their Self-Assessment claiming a £4,000 refund.
HMRC checks CIS returns. If the contractor filed nothing or filed incorrectly, HMRC temporarily withholds the subcontractor’s refund until the matter is corrected.

This is why I strongly encourage subcontractors to:

• Request CIS Deduction Statements monthly
• Cross-check them with payslips
• Keep copies safe for Self-Assessment

How CIS Deductions Are Used in Your Self-Assessment Tax Return

For sole traders, CIS deductions appear on the Self Employment Pages (SA103) in the “CIS Deductions” box.

Example scenario:

• Total subcontracting income: £38,000
• Allowable e