A subcontractor who registers for the Construction Industry Scheme has 20% deducted from payments, while one who does not register loses 30% [3]. Registration is free, the quickest route is online, and it requires two things above all: a Unique Taxpayer Reference and a Government Gateway account [1]. Those ten percentage points are the single strongest reason to get the process right before the first payment lands.
Registering for CIS is not one process but several, depending on whether the business pays subcontractors, is paid as a subcontractor, or does both. Contractors must register before taking on their first subcontractor, subcontractors choose whether to register but pay a higher rate if they do not, and many construction businesses have to register as both [6].
This guide walks through each route in order: who needs to register, what information to have ready, the exact steps for subcontractors and for contractors, what HMRC sends back, and the verification step that follows. It is written for construction sole traders, limited companies and the accountants who set them up.
Key takeaways
- Registering as a subcontractor drops the deduction rate from 30% to 20%, so it is worth doing before the first payment.
- Every applicant needs a Unique Taxpayer Reference (UTR) and a Government Gateway user ID to register online.
- Contractors must register before paying their first subcontractor, and receive an employer PAYE reference in return.
- A business that both pays and is paid for construction work must register as a contractor and a subcontractor.
- After registration, contractors must verify each subcontractor with HMRC before the first payment to confirm the correct deduction rate.
Who needs to register
CIS registration depends on the role the business plays, and the same business can play more than one [6]. The table below sets out who must register and who simply should.
| Role | Registration requirement | Consequence of not registering |
|---|---|---|
| Contractor | Must register before paying the first subcontractor | Cannot operate the scheme lawfully |
| Subcontractor | Not compulsory, but strongly advisable | Deduction rises from 20% to 30% |
| Both contractor and subcontractor | Must register as both | Higher deductions plus inability to operate as a contractor |
A contractor is any business that pays subcontractors for construction work, and registration is a legal requirement before the first payment [6]. A subcontractor is a business that carries out construction work for a contractor, and while it is not obliged to register, the 30% rate applied to unregistered subcontractors makes registration the sensible default [3]. Guidance for one-person construction businesses is set out on the Moonworkers payroll for sole traders pages.
Before starting: what to have ready
Whichever route applies, the registration form asks for a consistent set of details, and gathering them first makes the process quick [1]. The list below covers what a subcontractor needs to register online.
| Detail | Why it is needed |
|---|---|
| National Insurance number | Identifies the individual to HMRC |
| Unique Taxpayer Reference (UTR) | The core reference for CIS and self assessment |
| Government Gateway user ID | Required to access the online service |
| Turnover for the last 12 months | Used where gross payment status is also sought |
| Evidence of turnover (bank statements, invoices, deduction statements) | Supports the turnover figure |
| VAT number, if registered | Links the CIS record to VAT |
| Bank account details | For any repayments due |
| PAYE reference, if the business already employs staff | Links the CIS record to an existing scheme |
To use the online service a subcontractor needs a UTR, and to sign in it needs a Government Gateway user ID and password, which can be created during registration if none exists [1]. The exact matching of the business name and references matters later, because a contractor verifying the subcontractor must use details that match HMRC's record precisely [7].
Getting a UTR if you do not have one
A business without a UTR cannot register for CIS directly. The route is to register as a new business for self assessment first, and to choose the option for working as a subcontractor when prompted [1]. Doing so registers the business for both self assessment and CIS at the same time, which avoids a two-step delay [1]. This combined registration is the reason many new subcontractors are set up for CIS as a by-product of registering for self assessment [4].
How to register as a subcontractor
Registering as a subcontractor secures the standard 20% rate rather than the 30% higher rate, and the online service is the quickest route [1]. Online registration produces net payment status, also called payment under deduction, which is the standard position for most subcontractors [1].
Sole traders
A sole-trader subcontractor registers online through the CIS service using its UTR and Government Gateway sign-in [4]. Where the trader prefers paper, form CIS302 registers a sole trader as a subcontractor and can also be used to apply for gross payment status at the same time [4]. A postal route also exists specifically for registering under deduction, for traders who cannot use the online service [12].
The information required mirrors the checklist above, with the National Insurance number and UTR being the two identifiers HMRC uses to match the record [1]. Temporary National Insurance numbers, which begin with the letters TN or with two digits, cannot be used for verification later, so a genuine number is essential [7].
Limited companies and partnerships
A limited company registers as a subcontractor using form CIS305, which also allows the company to apply for gross payment status in the same submission [5]. A partnership uses form CIS304 for the equivalent purpose [8]. In both cases the company or partnership UTR is the key reference, alongside the company registration number for an incorporated business [7].
Because these routes double as gross payment status applications, a company or partnership that expects to qualify can register and apply for gross status in one step rather than registering under deduction and applying separately later [5]. The tests behind gross status are covered in the guide to CIS gross payment status. Accountants setting up several construction clients often handle these company and partnership registrations from a single multi-client payroll dashboard.
Registering by post
Postal registration remains available for subcontractors who cannot register online, using the relevant CIS form for the business type [12]. The trade-off is speed: a posted form takes longer to process than the online service, during which any payments received would suffer the 30% rate until the registration is matched [3]. For that reason the online route is preferable wherever it is available [1].
How to register as a contractor
A contractor must register for CIS before it pays its first subcontractor [2]. A sole trader, partnership or limited company that already has a UTR can register for CIS online, and can apply for gross payment status at the same time if it is also a subcontractor [2].
What HMRC sends back
On completing contractor registration, HMRC sends a letter containing the information needed to start operating as a contractor, including the employer PAYE reference number [2]. That reference is what the contractor uses to file its monthly CIS300 return and to pay deductions across to HMRC [11]. Without it, the contractor cannot report or remit the deductions it makes, so the letter is the practical trigger for beginning contractor operations [2].
If the business already employs staff
A construction business that already runs PAYE for employees does not set up a separate CIS scheme. Instead, HMRC converts the existing PAYE scheme into a combined PAYE and CIS scheme [2]. The business then makes a single monthly or quarterly payment covering PAYE tax, National Insurance and CIS deductions together [2]. This unified payment is why construction employers benefit from HMRC-recognised payroll software for SMEs that handles PAYE and CIS on the same record rather than reconciling two systems by hand.
Registering as both a contractor and a subcontractor
Many construction businesses pay other firms while being paid themselves, and these businesses must register in both capacities [3]. When acting as a contractor the business follows the contractor rules, and when acting as a subcontractor it follows the subcontractor rules, with the two roles reported separately [6].
Registering as both means completing the subcontractor registration to secure the 20% rate on incoming payments, and the contractor registration to operate the scheme on outgoing ones [2]. Overlooking the subcontractor side is a common error for firms that think of themselves primarily as contractors, and it leaves their own income exposed to the 30% deduction until they register [3].
Take a groundworks company that wins a contract from a main contractor while engaging its own labourers as subcontractors. As a subcontractor to the main contractor, it needs to be registered so that its invoices suffer 20% rather than 30%, and as a contractor to its labourers, it must be registered before paying any of them [6]. The two registrations are separate submissions but sit under the same business, and the deductions the company suffers can later be offset against the deductions and PAYE it owes as an employer [11]. Getting both registrations in place before the first job avoids the higher rate on income and the inability to operate the scheme on outgoing payments [2].
After registering: verification and the first payment
Registration alone does not set a subcontractor's deduction rate in a given contract. Before making a first payment, the contractor must verify the subcontractor with HMRC to confirm it is registered and to obtain the correct payment status [7]. Verification is done online, and the contractor signs in to the CIS service to complete it [9].
A successful verification returns a unique verification reference number and the rate to apply [7]. Where HMRC cannot match the subcontractor from the details supplied, the subcontractor is treated as unmatched and must suffer the 30% rate, usually because it has not registered or because the contractor entered its details incorrectly [7]. This is why accurate registration details matter so much: a mismatch at verification undoes the benefit of registering [9].
What details a subcontractor gives a contractor
When a registered subcontractor enters into a contract, it should give the contractor its legal name exactly as held on HMRC's system, together with its UTR and National Insurance number [6]. A limited company supplies its company name, company UTR and registration number, while a partnership supplies the nominated partner details, trading name and partnership UTR [7]. The details must match HMRC's record precisely, because verification compares them character by character [7]. Once verified and paid, the subcontractor receives payment and deduction statements it later uses to reclaim the tax, as explained in the guide to what CIS tax is.
Common registration mistakes
The most expensive registration mistake is simply not registering as a subcontractor, which leaves income exposed to the 30% rate rather than 20% [3]. The second is a mismatch between the details a subcontractor registers with and the details a contractor uses to verify, which produces an unmatched result and the higher rate even though the subcontractor is registered [7].
A third is a contractor beginning to pay subcontractors before registering, which breaches the requirement to register first and leaves the contractor unable to report deductions correctly [2]. A fourth is using a temporary National Insurance number, which cannot be verified and so forces the higher rate [7]. Each of these is avoidable with accurate details and registration ahead of the first payment [6].
How payroll software fits in
Registration is a one-off event, but the obligations it triggers are continuous. A contractor must verify each new subcontractor, apply the right rate, file a monthly CIS300 and pay deductions on the PAYE cycle, all of which flow from the registration [11]. Handling those steps by hand is manageable for a single subcontractor but error-prone across many [6].
Software that treats CIS as a native part of payroll verifies subcontractors, applies the correct rate after materials, files returns and reflects deductions in the combined PAYE and CIS scheme from one record. Moonworkers provides this for construction businesses running payroll for SMEs, and exposes the same logic for platforms building their own tooling through its HMRC-recognised payroll API.
Conclusion
Registering for CIS is straightforward once the roles are clear: a contractor registers before paying anyone, a subcontractor registers to secure the 20% rate, and a business that does both registers twice. The two things that make or break the process are having a UTR and a Government Gateway account ready, and supplying details that will match exactly when a contractor later verifies the subcontractor.
The registration itself is only the entry point. The value comes from operating the scheme cleanly afterwards, with accurate verification, correct rates and timely returns, because that is what keeps deductions at 20% rather than 30% and, for those who qualify, opens the door to gross payment status. Construction businesses that treat registration as the start of a joined-up payroll and reporting routine, rather than a form to file once, are the ones that avoid the higher rate and the penalties that follow careless CIS.
Frequently asked questions
Do I have to register for CIS as a subcontractor?
Registration is not legally compulsory for a subcontractor, but it is almost always worth it. An unregistered subcontractor has 30% deducted from its payments, while a registered one has 20%. The extra ten percentage points are recoverable later, but registering avoids tying up that cash through the year. Registration is free and quickest online.
What do I need to register for CIS online?
A subcontractor needs a Unique Taxpayer Reference (UTR) and a Government Gateway user ID and password, which can be created during registration. The form also asks for a National Insurance number, turnover for the last 12 months, evidence of that turnover, a VAT number if registered, bank account details, and a PAYE reference if the business already employs staff.
How do I register for CIS if I do not have a UTR?
A business without a UTR should register as a new business for self assessment first and choose the option for working as a subcontractor when prompted. This registers the business for both self assessment and CIS at the same time, so no separate CIS registration is needed. The UTR then follows from the self-assessment registration.
What happens after I register as a CIS contractor?
HMRC sends a letter with the information needed to start operating, including the employer PAYE reference number used to file returns and pay deductions. If the business already runs PAYE, HMRC converts the existing scheme into a combined PAYE and CIS scheme, and the business makes one monthly or quarterly payment covering PAYE, National Insurance and CIS deductions together.
