What is CIS and Who Needs to Register?

What is CIS? For many construction businesses and tradespeople, it is the point where tax stops feeling like a year-end job and starts affecting every payment that comes in or goes out.

CIS stands for the Construction Industry Scheme. It is an HMRC scheme that sets rules for how contractors pay subcontractors for construction work in the UK. In simple terms, contractors may have to deduct money from a subcontractor’s labour payment and send it to HMRC as an advance payment towards that subcontractor’s tax and National Insurance bill.

That sounds straightforward until you are the person trying to work out whether you count as a contractor, a subcontractor, or both. That is where mistakes usually start.

Why CIS Catches Out Good Construction Businesses

The awkward part of CIS is that it is not only for large building firms. It can apply to sole traders, limited companies, partnerships, contractors, subcontractors and businesses that do not think of themselves as “construction companies” every day.

A builder who pays other trades can be a contractor. A plumber working for a building firm can be a subcontractor. A limited company can be both on the same project, paying subcontractors on one job while being paid as a subcontractor on another.

At Brickbooks and Payroll, we see the same pattern often: the work is real, the invoices are being raised, but the CIS position has not been checked early enough. That can lead to incorrect deductions, missing monthly returns, awkward conversations with subcontractors and avoidable HMRC pressure.

If you are already looking for local help, our team supports tradespeople and construction businesses with CIS tax help in Bedford and across the wider UK.

What CIS Means in Plain English

Under CIS, the contractor checks the subcontractor’s tax status with HMRC before paying them. HMRC then confirms whether deductions should be made from the subcontractor’s payment.

GOV.UK explains that CIS payments must take account of the subcontractor’s tax status, and deductions may need to be made from the part of the payment that is not for materials.

The usual deduction rates are:

• 20% for registered subcontractors
• 30% for unregistered subcontractors
• 0% where the subcontractor has gross payment status

Those deductions are not an extra tax in themselves. They are advance payments towards the subcontractor’s tax and National Insurance bill. For subcontractors, that makes registration important because being unregistered can mean a larger deduction from payments.

Who Needs to Register for CIS?

You usually need to register as a contractor if your business pays subcontractors for construction work. This could include building, alterations, repairs, decorating, demolition, site preparation, installation work and other construction operations.

You usually need to register as a subcontractor if you do construction work for a contractor and you are not being treated as an employee for that work.

Some businesses need to register as both. That is common in construction. For example, a small building company may take on subcontracted work from a main contractor, then pay a plasterer, electrician or roofer to complete parts of the job. In that case, the business may have responsibilities in both directions.

This is where we would make a practical judgement call. Do not only ask, “Am I in construction?” Ask:

• Do we pay other people or businesses to carry out construction work?
• Do we get paid by another contractor for construction work?
• Are labour and materials split clearly on invoices?
• Have subcontractors been verified before payment?
• Are monthly CIS returns being filed on time?

Those questions usually reveal the real answer faster than reading another generic definition.

Suggested read: CIS Accountant for Subcontractors: Fast, Reliable & HMRC Compliant

Contractors, Subcontractors and the Grey Area Between Them

A contractor under CIS is not just someone with a hard hat and a big project. It is a business that pays subcontractors for construction operations. A subcontractor is a person or business paid by a contractor to carry out construction work.

The grey area appears when a business grows. A sole trader may start by working on sites for other companies. Then they take on bigger jobs, bring in another trade, and suddenly they are also paying someone else. That change matters.

If you only register as a subcontractor but then start paying other subcontractors, you may miss contractor duties. These can include verifying subcontractors, making the right deductions, giving payment and deduction statements, paying deductions to HMRC and filing monthly returns.

For businesses operating in Buckinghamshire or nearby areas, we also provide CIS tax help in Milton Keynes for contractors and subcontractors who need the rules translated into day-to-day actions.

What Happens If You Do Not Register?

If you are a subcontractor and you do not register for CIS, contractors may deduct 30% from your labour payments instead of 20%. That can hit cashflow hard, especially when materials, fuel, insurance and wages still need paying.

If you are a contractor and you fail to register or manage CIS correctly, the problem is different. You may have missed verification, deducted the wrong amount, failed to file returns or paid HMRC late. None of that gets easier because the business was busy.

Our view is simple: CIS is a cashflow and compliance issue, not just a tax admin task. A construction business can be profitable on paper and still feel squeezed if deductions, returns and records are not handled properly.

HMRC’s own guidance on contractor deductions confirms that CIS deduction rates are 20% for registered subcontractors, 30% for unregistered subcontractors and 0% for gross payment status.

What Records Should You Keep?

Good CIS records protect both sides. Contractors need enough information to show who was paid, how they were verified, what was deducted and what was reported. Subcontractors need records that show the deductions already taken from their pay.

At a minimum, keep:

• subcontractor verification details
• invoices showing labour and materials separately
• payment and deduction statements
• monthly CIS return records
• bank payment records
• UTRs, National Insurance numbers, and company details where relevant

This is one reason we build workflows around accounting software rather than leaving CIS as a pile of paperwork. Brickbooks and Payroll works with tools including QuickBooks, Xero, FreshPay, Nest Pensions, NOW Pensions, and Syft, so the records can support the business instead of becoming another monthly headache.

For construction firms with wider payroll duties, CIS often sits alongside PAYE, pensions, and subcontractor checks. If that sounds familiar, our CIS tax help in St Albans page explains how we support trades businesses across Hertfordshire too.

FAQ

Is CIS the Same as PAYE?

No. CIS applies to payments made by contractors to subcontractors for construction work. PAYE is used for employees, so the right treatment depends on the working arrangement, not just the job title.

Do Sole Traders Need to Register for CIS?

Yes, a sole trader may need to register if they work as a subcontractor in construction or pay subcontractors for construction work. The exact role matters because a sole trader can be a subcontractor, a contractor, or both.

Does CIS Apply to Materials?

CIS deductions are usually made from the labour element, not the cost of materials. This is why invoices should separate labour and materials clearly, especially where a contractor is calculating deductions.

Can a Subcontractor Get CIS Deductions Back?

CIS deductions count as advance payments towards tax and National Insurance. If too much has been deducted across the tax year, this is usually dealt with through the subcontractor’s tax return or company tax process.

What Do You Need Before Registering as a Subcontractor?

You will usually need your UTR and, for sole traders, your National Insurance number. GOV.UK says subcontractors can register online, and if they do not have a UTR, they can register as a new business for Self Assessment and CIS at the same time.

CIS is manageable once the roles, records and monthly process are clear. The risk is leaving it until a contractor asks for details, a payment is deducted at the higher rate, or HMRC starts chasing missing returns.

Need Help With CIS?

If you are not sure whether you need to register, or you already have CIS returns to file, it is worth getting the process checked before it becomes a bigger issue.

At Brickbooks and Payroll, we help contractors, subcontractors and construction SMEs with CIS returns, bookkeeping, payroll, VAT, self-assessments and year-end accounts. We work digitally, but with a practical, no-nonsense approach shaped by more than 15 years of specialist experience in trades and construction accounting.

To speak to us, call 01234 481591, email info@brickbooksandpayroll.com, or book your free consultation.