CIS registration means telling HMRC you work as a construction subcontractor, so contractors deduct 20% from your pay instead of 30%. You register online through your Government Gateway account, or by phone or post.
If you are starting work as a subcontractor in UK construction, registering under the Construction Industry Scheme should be one of your first jobs.
The lower 20% deduction improves your cash flow straight away and makes it easier to claim a rebate at the end of the tax year.
At R&R Chartered Certified Accountants, we help new and existing subcontractors across Lancashire register correctly and avoid the common mistakes that delay payments or reduce rebates. This guide walks you through it step by step.
Once you are registered, the ongoing returns and rebate claims are the part most subcontractors would rather not handle alone. That is what our CIS accountant service is for, alongside our work as accountants for construction and engineering businesses.
Why Should You Register for CIS?
Registering for CIS as a subcontractor is voluntary, but if you do not register, contractors must deduct tax at the higher 30% rate. Once registered, HMRC tells contractors to deduct tax at the lower 20% rate rather than the default 30%.
The difference is significant. On a £2,000 labour invoice, an unregistered subcontractor loses £600 upfront and a registered one loses £400.
Over a year, that extra 10% can add up to thousands of pounds tied up with HMRC until you file your self assessment tax return.
Who Needs to Register?
You should register as a CIS subcontractor if:
- You do construction work for a contractor.
- You are self-employed, a partner in a partnership, or the owner of a limited company.
- You work in a trade covered by CIS, such as building, plumbing, electrical work, plastering, roofing, groundwork or decorating.
If you are a limited company, the company registers separately. If you are self-employed, you register as an individual under your Unique Taxpayer Reference.
What Do You Need Before You Register?
Before starting the registration, make sure you have:
- Your National Insurance number.
- Your Unique Taxpayer Reference if you already file a tax return.
- Your business name, trading address and contact details.
- The date you started working as a subcontractor.
If you have not yet registered for self assessment, you should do that first or at the same time.
How Do You Register for CIS Online?
- Go to the HMRC online services page and sign in or create a Government Gateway account.
- Navigate to the Construction Industry Scheme registration section.
- Enter your personal or business details, including your National Insurance number and UTR.
- Confirm that you are registering as a subcontractor.
- Submit the registration and wait for HMRC confirmation, which usually arrives within a few working days.
You can also register by phone or post if you can’t use the online service.
Once you are registered, each contractor verifies you with HMRC before paying you, using details such as your name, UTR and National Insurance number. HMRC then tells the contractor which rate to deduct.
What Happens After Registration?
Once registered, HMRC will confirm your status. You should then:
- Tell any contractors you work for that you are CIS-registered.
- Provide your UTR and National Insurance number when asked.
- Keep all CIS payment and deduction statements.
- Make sure your self assessment tax return is filed each year to claim any rebate.
What CIS Registration Mistakes Should You Avoid?
- Registering too late: Contractors may deduct 30% from your first payments if registration is delayed.
- Using the wrong entity: A sole trader and a limited company are registered differently.
- Missing the self assessment link: CIS registration does not replace self assessment registration.
- Not keeping statements: You need these to prove deductions and claim rebates.
- Forgetting the contractor side: if you also pay other subcontractors for construction work, you must register as a contractor as well.
You can complete the process on the official HMRC CIS subcontractor registration page. If you are not yet registered as self-employed, start with registering for Self Assessment on GOV.UK.
Frequently Asked Questions
Online registration is usually confirmed within a few working days. Postal applications can take several weeks.
Yes, if you are self-employed. CIS registration is separate from self assessment registration, and you need both to report your income and claim rebates.
Yes. Limited companies that do construction work as subcontractors register under CIS using their company UTR and accounts office reference.
Check that your registration is active and that you have given the contractor your correct UTR and National Insurance number. If the issue continues, contact HMRC.
Yes for a limited company: an authorised agent such as your accountant can register the company with HMRC. Sole traders normally register themselves, either online through their Government Gateway account or on paper form CIS301, and an accountant can prepare the details and guide you through it.
The Bottom Line
CIS registration is one of the simplest ways to improve your cash flow as a subcontractor. The 10% gap between registered and unregistered deductions adds up quickly, and being registered also makes your annual rebate easier to claim.
If you need help registering for CIS, setting up Self Assessment or understanding how the scheme affects your tax, contact R&R Chartered Certified Accountants for a free consultation.
Tax figures checked by Rehan Razzaq FCCA on 8 October 2026 for the 2026/27 tax year.
This article is general guidance for UK businesses and individuals and does not constitute personal financial or tax advice. Rules, thresholds and individual circumstances vary — always confirm your specific position with a qualified accountant before acting.
Rehan Razzaq, FCCA
Founder, R&R Chartered Certified Accountants
ACCA Chartered Certified and Xero Certified Advisor, helping UK small businesses and subcontractors with accounts, tax and financial planning since 2021.
We work with clients right across Lancashire and the North West. If you are looking for accountants in Blackburn, or a local accountant in Nelson or accountant in Accrington, our team is a short drive away.
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