Why Register for CIS?
If you work in the UK construction industry as a subcontractor, registering for the Construction Industry Scheme (CIS) is one of the most important things you can do for your cash flow.
Unregistered subcontractors have 30% deducted from their labour payments by contractors and paid directly to HMRC. Registered subcontractors only have 20% deducted. On a £3,000 labour invoice, the difference is £300 — money that stays in your pocket until your Self Assessment return rather than sitting with HMRC.
Registration is free. It takes around 10 minutes online. There is no good reason not to do it.
What You Need Before You Register
Before starting the registration process, make sure you have:
For sole traders:
- Your UTR (Unique Taxpayer Reference) — 10-digit number from HMRC
- Your National Insurance number
- Your full legal name and trading name (if different)
- Your business address
- Access to the Government Gateway (or you'll create one during registration)
For limited companies:
- Company UTR
- Company registration number (from Companies House)
- Registered company name and address
- Government Gateway login for the company
For partnerships:
- Partnership UTR
- Each partner's individual UTR and NI number
- Government Gateway login
Don't Have a UTR Yet?
If you haven't done a Self Assessment return before, you may not have a UTR. You can get one by registering for Self Assessment first at gov.uk/register-for-self-assessment. HMRC will post your UTR within 10 working days.
How to Register Online (Step by Step)
Step 1: Go to the Government Gateway
Visit gov.uk/government-services and search for "Register as a subcontractor." You will be directed to HMRC's online services portal.
Step 2: Sign In or Create a Government Gateway Account
If you already file Self Assessment online, you have a Government Gateway account. Use those credentials. If not, create a new account — you'll need an email address and a mobile number for two-factor authentication.
Step 3: Access CIS Registration
Once logged in, select "Construction Industry Scheme" from the list of services, then choose "Register as a subcontractor."
Step 4: Provide Your Details
Enter:
- Your UTR number
- Your National Insurance number (sole traders)
- Your business name and address
- Your bank details (for verification purposes)
Step 5: Confirm and Submit
Review all details carefully before submitting. HMRC will confirm your CIS registration within a few minutes for online registrations. Your UTR will now show in HMRC's CIS database when contractors verify you.
Registering by Phone
If you prefer to register by phone, call HMRC's CIS helpline:
0300 200 3210 (Monday to Friday, 8am to 6pm)
Have your UTR, NI number, and business details ready. Phone registration takes around 15–20 minutes.
What Happens After Registration
Once registered, HMRC adds your details to their CIS database. When a contractor verifies you for the first time, HMRC will confirm:
- That you are registered
- Your applicable deduction rate (20% for standard registration)
The contractor then applies 20% to your labour invoices instead of 30%.
Do You Need to Tell Your Current Contractors?
Yes. If you are already working with contractors who have been deducting at 30%, tell them you have now registered and ask them to re-verify you with HMRC. They should update your rate to 20% for future payments. The 30% already deducted will be credited through your Self Assessment return.
Self Assessment: You Still Need to File
CIS registration does not replace your obligation to file a Self Assessment tax return each year. The deductions made by contractors are advance payments — your actual tax liability is calculated on your Self Assessment return. If the deductions exceed your tax bill, HMRC will refund the difference.
Make sure you also register for Self Assessment if you haven't already. Subcontractors with income above £1,000 must file.
CIS Registration for Limited Companies
A limited company subcontractor registers separately from any individual director. The company will have its own UTR (issued by Companies House when the company is formed). You register the company, not yourself personally, as the CIS subcontractor.
Important: The company still files its own corporation tax return. CIS deductions suffered by the company can be offset against the company's PAYE and NI obligations, which often results in monthly refunds from HMRC.
What if You Are Both a Contractor and a Subcontractor?
Many businesses in construction act as both. You may subcontract to larger main contractors while also employing or subcontracting your own workers. In this case, you must register as both a contractor and a subcontractor. The processes are separate, but you manage both through the same Government Gateway account.
Penalties for Not Registering
There are no direct fines for being an unregistered subcontractor — you simply have 30% deducted instead of 20%. However, failing to register for Self Assessment (which is separate but related) carries penalties of up to £1,600 for persistent non-compliance.
For contractors, failing to register or file monthly returns correctly carries penalties starting at £100 per month per return.
Using FlashBill Once You're Registered
Once you have your CIS registration and UTR, FlashBill makes invoicing simple. Add your UTR to your account, set the CIS rate for each client, and every invoice is calculated and formatted correctly. No spreadsheets, no manual maths.