Construction Industry Scheme (CIS) Guide for UK Trade Businesses — Deductions, Registration and Compliance (2026)

What is the Construction Industry Scheme?

CIS is an HMRC scheme that requires contractors to deduct money from payments to subcontractors and pass it directly to HMRC as an advance payment toward the subcontractor's tax liability. It was introduced because cash-in-hand working — with no tax ever paid — was endemic in construction. By making contractors responsible for deducting and remitting the tax, HMRC moved the compliance obligation up the chain to the party most visible to the tax authority.

The deducted amounts are not a separate construction tax. They are a prepayment of Income Tax (for sole traders and partners) or Corporation Tax (for limited companies). At the end of the tax year the subcontractor reconciles the deductions against their actual liability and either pays the remainder or claims a refund. CIS deductions taken in excess of actual liability are refunded by HMRC — the scheme does not result in double taxation, only earlier collection.

The scheme applies across the UK, including Scotland and Wales. It is administered by HMRC and is entirely separate from other industry schemes such as the CITB levy.

What counts as construction work under CIS?

"Construction operations" under CIS are defined broadly. The scheme covers:

• Construction, alteration, repair, extension, and demolition of buildings and structures
• Civil engineering works: roads, bridges, tunnels, sewers, pipelines, drainage
• Installation of systems within buildings: heating, lighting, power, water, ventilation, air conditioning, drainage
• Plumbing and gas fitting
• Electrical installation and testing
• Carpentry, joinery, plastering, tiling, painting, decorating
• Scaffolding and temporary structures
• Groundwork, foundations, and excavation
• Roofing, cladding, glazing
• Preparatory work directly enabling any of the above
• Cleaning of the inside of buildings as part of construction or renovation

CIS does not apply to:

• Professional services: architecture, surveying, engineering design, project management
• Manufacture or delivery of materials — if there is no labour element on site, CIS does not apply
• Mining, quarrying, and extraction of natural resources
• Manufacture of components (windows, doors, structural steel) off-site, even if later installed on site
• Work directly for a private homeowner as the end user (a plumber hired by a homeowner directly is not in CIS for that job)

The key test is whether construction operations are being carried out under a contract. If there is no construction operation, there is no CIS obligation — regardless of the size of the payment.

Who does CIS apply to: contractors and subcontractors

The scheme has two defined roles. The same business can be both simultaneously — main contractors operating in the middle of a supply chain are contractors to their own subcontractors and subcontractors to the developer or client above them.

The £1 million rule catches businesses outside traditional construction. A supermarket chain spending heavily on store fit-outs, a manufacturer building a new facility, or a property company carrying out large-scale refurbishments can all be drawn into the contractor role — even if construction is entirely incidental to their main trade.

CIS does not apply to employees. If a person is employed by a business — with PAYE deducted from their wages — CIS is irrelevant to that relationship. The scheme only applies to self-employed subcontractors paid under a contract for services, not a contract of employment. Whether a worker is genuinely self-employed or should be treated as an employee is a separate question (covered under employment status rules and IR35 for limited companies) but it is one that has significant overlap with CIS.

Contractor obligations: verify, deduct, report, pay

If you pay subcontractors for construction work, registering as a CIS contractor creates four ongoing obligations.

1. Verify before you pay

Before making any payment to a new subcontractor, you must verify them with HMRC. Verification is done online through HMRC's CIS service, by phone, or via accounting software that supports CIS. You provide the subcontractor's name, UTR, and company registration number (if a limited company). HMRC responds immediately with the deduction rate to apply: 0%, 20%, or 30%.

Keep the verification reference number HMRC gives you. It is evidence that you applied the correct rate. You do not need to re-verify the same subcontractor for every payment — one verification per subcontractor per contractor relationship is sufficient unless their details change. But each contractor must verify independently; a subcontractor being registered with 20 other contractors does not affect your obligation.

Failure to verify before payment carries a penalty of between £100 and £3,000 per instance depending on the size of the payment involved. If you paid at 20% when HMRC would have said 30%, you are personally liable for the shortfall.

2. Deduct at the correct rate

CIS deductions are calculated on the labour and plant element of the invoice only — not on materials. If the subcontractor separates labour and materials on their invoice, you deduct CIS from the labour figure only. If no separation is made, HMRC expects you to deduct CIS from the full payment, which penalises the subcontractor unnecessarily. As a contractor it is worth asking subcontractors to itemise their invoices correctly.

The deducted amount must be paid to HMRC by the 19th of the following month (or 22nd for electronic payment), alongside your monthly CIS300 return.

3. Give subcontractors a payment and deduction statement

By the 19th of the month following payment, you must give each subcontractor a written payment and deduction statement. This shows the gross amount, the materials element (if any), the deduction rate applied, and the amount deducted. Subcontractors use these statements to reclaim their deductions through Self Assessment or Corporation Tax. Without them, the subcontractor cannot prove what was deducted.

4. Submit the monthly CIS300 return

The CIS300 is a monthly return filed with HMRC listing every subcontractor paid in the tax month (6th to 5th), the gross amounts, materials costs, and deductions. It must be submitted by the 19th of each month, even if you made no payments — a nil return is required whenever you are registered as a contractor and have not formally suspended your registration.

The three CIS deduction rates

Every CIS subcontractor is subject to one of three rates. The applicable rate is confirmed by HMRC at the point of verification.

The 30% rate is often a surprise. It applies not only to subcontractors who have never registered but also to any subcontractor whose details HMRC cannot match — a name spelled differently, a UTR that belongs to a different business structure, a company number that has changed since registration. If HMRC cannot verify the details provided, they default to 30%. The subcontractor will not be told directly that this has happened — they only find out when they see a larger-than-expected deduction on their statement.

If you are a subcontractor and a contractor tells you the 30% rate applied, contact HMRC to find out why verification failed. Do not assume it will resolve itself. Every month at 30% rather than 20% costs you money that you eventually get back, but which is unavailable to you in the meantime.

Subcontractor registration: how to get the 20% rate

Registering as a CIS subcontractor takes around 15 minutes via your Government Gateway account at HMRC.gov.uk. Before you can register you need:

• A Unique Taxpayer Reference (UTR) — the 10-digit number issued when you register for Self Assessment. If you don't have one, register for Self Assessment first and allow 10 working days for the UTR to arrive.
• Your National Insurance number
• Your business name and legal structure
• For limited companies: the company registration number from Companies House

Once registered, give your UTR to every contractor before they make their first payment. They verify it with HMRC and the 20% rate is confirmed. Subcontractor registration does not expire automatically, but your rate can change if your compliance record deteriorates.

The financial case for registering promptly is straightforward. On £50,000 of annual labour invoicing, the difference between 20% and 30% deduction is £5,000 per year in cash that you do not have access to until your tax return is processed. Registering before you start work costs nothing and takes less time than a morning coffee.

Gross payment status: getting paid in full

Gross payment status (GPS) means contractors pay you the full invoice amount with no CIS deduction. You account for your own tax through Self Assessment or Corporation Tax in the normal way, rather than having 20% withheld on every labour payment throughout the year.

The cash flow benefit is significant. A subcontractor billing £150,000 in labour per year keeps an extra £30,000 in their bank account throughout the year rather than lending it to HMRC at 0% interest. The tax is still paid — just at the end of the year rather than monthly.

The three GPS tests

To qualify, all three of the following must be met:

To apply, use the CIS online service in your Government Gateway account. HMRC reviews your tax record and responds. If approved, the status applies immediately — contractors who verify you from that point will be told 0% applies.

HMRC reviews GPS annually. A compliance slip — a late Self Assessment return, a missed VAT payment — can result in status being withdrawn. If that happens, contractors will see a reversion to 20% the next time they verify you, which can come as an unpleasant surprise mid-project.

If you have been registered for CIS for at least 12 months and have a clean compliance record, it costs nothing to check whether you meet the turnover test and apply. There is no reason to delay.

The materials exclusion: why invoice format matters

CIS deductions apply to the labour and plant element of a subcontractor's invoice only. The cost of materials supplied and used in the construction work is excluded from the CIS calculation, provided those materials are not marked up beyond a normal commercial margin.

This means a subcontractor who supplies both labour and materials should always separate them clearly on their invoice. If the invoice shows a single lump sum with no breakdown, the contractor must deduct CIS from the whole amount — including the materials portion. That is money the subcontractor does not need to lose.

In the example above, a correctly formatted invoice means £240 more cash in the subcontractor's pocket on this single invoice. The materials exclusion does not reduce the subcontractor's total tax liability — they still declare all income in their tax return — but it does mean less cash is withheld each month and the subcontractor has better cash flow throughout the year.

Materials that are marked up substantially beyond cost may be treated by HMRC as part of the labour charge. Keep material costs at a normal commercial level or be able to evidence the actual cost with supplier invoices.

How subcontractors reclaim CIS deductions

CIS deductions are not additional tax — they are an advance against your existing tax liability. At the end of the tax year, you reconcile the deductions made against what you actually owe, and any excess is refunded.

Sole traders and partners reclaim through Self Assessment. Your tax return asks for the total CIS deductions made in the year (taken from your payment and deduction statements). HMRC offsets those against your Income Tax and Class 4 NI liability. If deductions exceed the liability, the refund is issued — usually within a few weeks of filing. Filing early in the tax year (April or May) speeds this up considerably.

Collect payment and deduction statements from every contractor throughout the year. Do not wait until January to look for them. If a statement is missing, contact the contractor — they are legally required to provide it.

Limited companies have two routes. The most useful in-year option is to offset CIS deductions suffered against the company's PAYE/NI liabilities to HMRC. Each month, if your company deducts income tax and NI from employees and pays it over, you can reduce that payment by the CIS deducted from your income during the same period. This keeps cash in the business rather than waiting months for a year-end refund. If CIS deductions exceed the PAYE/NI liability in a month, the excess carries forward. Companies whose CIS deductions substantially exceed their PAYE bill can apply to HMRC for a monthly repayment instead. Speak to your accountant about setting up the offset arrangement.

CIS and VAT: the Domestic Reverse Charge

Since 1 March 2021, VAT-registered businesses in the construction supply chain must apply the VAT Domestic Reverse Charge (DRC) to most CIS-regulated supplies. Understanding how DRC interacts with CIS is essential for any trade business above the VAT threshold.

Under normal VAT rules, the subcontractor charges VAT on their invoice and the contractor pays it, then reclaims it as input tax. Under DRC, the subcontractor does not charge VAT on their invoice. Instead, the contractor — the recipient of the supply — accounts for the VAT directly on their own VAT return, as both output tax and (assuming full VAT recovery) as input tax. The net result for the contractor is no actual VAT cost, but the cash flow benefit of receiving VAT from the subcontractor is removed.

When DRC applies

DRC applies when all of the following are true:

• Both the supplier (subcontractor) and recipient (contractor) are VAT registered
• Both are CIS registered
• The supply is a CIS-defined construction operation (standard or reduced rate — zero-rated supplies are excluded)
• The recipient is not the end user of the building

Who is excluded from DRC

End users and intermediary suppliers are excluded. An end user is the final consumer of the building work — an owner-occupier, a landlord using the building themselves, or a business having work done on their own premises who does not onward supply the construction services. These businesses notify their subcontractor in writing that they are an end user, and normal VAT applies.

Landlords and housing associations receiving construction work for property they then let out are typically end users. However, if a developer is selling the constructed property onward as part of their trade, DRC applies.

DRC invoicing requirements

When DRC applies, the subcontractor's invoice must include the following:

• A statement that DRC applies, such as "Reverse charge: customer to account for VAT to HMRC"
• The VAT rate that would have applied (e.g. 20%)
• The VAT amount (shown for reference but not charged)
• The net amount (excluding VAT)

The subcontractor does not collect or pay this VAT. The contractor adds it to box 1 of their VAT return (output tax) and simultaneously reclaims it in box 4 (input tax). For most VAT-registered contractors making fully taxable supplies, this is tax-neutral. The impact falls mainly on subcontractors, who can no longer use VAT collected from contractors as working capital between collection and quarterly payment to HMRC.

Businesses that previously relied on the VAT float — collecting VAT in January and paying it to HMRC in late April — lose that benefit entirely under DRC. Plan cash flow accordingly.

Common mistakes and how to avoid them

Treating employees as subcontractors

The most serious CIS mistake is using the scheme to pay workers who should legally be classified as employees. If HMRC determines a worker is an employee rather than a genuine self-employed subcontractor, CIS does not apply to those payments — PAYE should have been operated instead. The contractor becomes liable for the PAYE income tax and National Insurance that should have been deducted, plus interest and penalties. This is distinct from IR35, which applies specifically to limited company contractors, but the employment status question is the same underlying issue.

HMRC's CEST tool can help assess employment status. Key indicators of employment include: the worker cannot send a substitute, the contractor controls how and when work is done, the worker has no financial risk, and the worker works exclusively for one contractor. If in doubt, take advice before the engagement begins.

Paying without verifying first

Every first payment to a new subcontractor must follow verification. Paying before verifying means you have no HMRC-confirmed rate, no verification reference, and no protection if the rate turns out to be 30%. The penalty for failing to verify is £100 to £3,000. It takes two minutes online and should be the first step in any new subcontractor engagement.

Missing nil returns

Monthly CIS300 returns are required even when no payments were made. Contractors who don't use subcontractors in a quiet month frequently skip the return, assuming there is nothing to file. The £100 penalty applies regardless. Set a recurring calendar reminder for the 19th of every month for as long as you are registered as a contractor. If you know you will have a long period of inactivity, formally notify HMRC so they suspend the return requirement.

Not providing payment and deduction statements

Contractors must issue a written deduction statement each time they make a CIS deduction, by the 19th of the following month. Failing to do so is a penalty offence and leaves subcontractors unable to reclaim their deductions correctly. For contractors using invoicing software, this should be an automated part of the payment process.

Sole traders not claiming deductions on Self Assessment

A surprising number of sole trader subcontractors fail to claim CIS deductions on their tax return — either because they cannot find their deduction statements or because they do not know where to enter the figures. The result is overpaying tax by the exact amount deducted. Keep every deduction statement in a single folder throughout the year and hand the full set to your accountant when preparing your return.

Not separating labour and materials on invoices

Invoicing a lump sum with no breakdown forces the contractor to deduct CIS from everything. Itemising labour and materials separately — which takes 30 seconds to set up in any invoicing software — means deductions apply only to the labour portion. For subcontractors supplying significant materials, this is a meaningful cash flow difference.

CIS penalties: what they cost

HMRC issues penalties for a range of CIS failures. The main ones affecting trade businesses are:

Penalties can be appealed if you have a reasonable excuse — unexpected illness, a bereavement, or HMRC system failure that prevented filing. A genuine administrative oversight without a reasonable excuse is unlikely to succeed on appeal. The best protection is a calendar system that ensures monthly returns are never missed.

How Trade2Base helps CIS-regulated construction businesses

CIS compliance is the administrative layer. Growing a profitable construction business requires knowing which marketing channels are actually bringing in the best construction contracts — the high-value jobs, the repeat clients, the commercial relationships worth investing in.

Trade2Base tracks where every enquiry comes from — Google, Checkatrade, word of mouth, repeat clients — and links it through to won jobs and revenue. For CIS-regulated contractors winning work on construction sites, that means knowing whether your Google Ads budget is generating the commercial groundwork contracts you want, whether the investment in Checkatrade is producing plumbing subbies work or domestic one-offs, and whether your repeat client relationships are worth the time you put into them.

When you know which sources produce your best construction contracts, you can put your marketing budget where it actually returns. That is a better use of time than guessing — and it compounds as your business grows.