What is the Construction Industry Scheme (CIS)

At Towerstone Accountants we provide specialist CIS accountancy services for contractors and construction businesses across the UK. We created this webpage for subcontractors and contractors who want clear guidance on the Construction Industry Scheme, including registration, deductions, refunds, and ongoing reporting obligations. Our aim is to help you stay compliant with HMRC, avoid costly errors, and understand how CIS affects your tax position.

If you work in construction in the UK, either as an individual or through a business, you will almost certainly come across CIS at some point. In my experience, CIS is one of the most misunderstood parts of the UK tax system, largely because it sits slightly outside what people think of as normal tax, and because it affects sole traders, limited companies, contractors, and subcontractors in different ways.

CIS stands for the Construction Industry Scheme. It is a HMRC scheme designed to collect tax from the construction industry in a way that reduces tax evasion and improves compliance, but it does so by shifting some of the responsibility for tax collection away from the worker and onto the contractor. That single design choice is what creates most of the confusion.

In this article I will explain what CIS is, who it applies to, how it works in practice, how deductions are made, how tax is eventually settled, and why CIS is not a tax in its own right, even though it often feels like one. I will also cover the most common misunderstandings I see and how CIS fits into the wider UK tax system.

The purpose of the Construction Industry Scheme

To understand CIS properly, it helps to understand why it exists. The construction industry has always had a high proportion of subcontractors, short term contracts, and mobile workers, which historically made it difficult for HMRC to ensure tax was being declared and paid correctly.

Rather than relying entirely on individuals to declare income at the end of the year, HMRC introduced CIS to collect tax earlier, at the point where money changes hands. Contractors deduct tax from payments to subcontractors and pay it directly to HMRC. This reduces the risk of tax going unpaid and smooths cash flow for the Exchequer.

From HMRC’s point of view, CIS improves compliance. From the subcontractor’s point of view, it often feels like money is being taken before they have had a chance to work out their actual tax position, which is why understanding how CIS is reconciled later is so important.

Who CIS applies to

CIS applies to construction work carried out in the UK. It affects businesses and individuals who work as contractors, subcontractors, or sometimes both.

In broad terms:.

• Contractors are businesses that pay others for construction work

• Subcontractors are businesses or individuals who are paid to carry out construction work

You do not need to be a large construction firm to fall under CIS. Many small businesses, property developers, and even landlords can be classed as contractors if they spend enough on construction work.

Subcontractors can be sole traders, partnerships, or limited companies. CIS applies regardless of business structure, although the way tax is later settled differs depending on whether you are self employed or incorporated.

What counts as construction work under CIS

Construction work under CIS is defined quite widely. It includes things most people would expect, such as building, alterations, repairs, and demolition, but it also includes preparatory work and finishing work.

Examples include bricklaying, groundworks, roofing, plastering, decorating, electrical work, plumbing, and many types of site preparation. It also includes labour supplied with materials, which is an important point for invoicing.

There are also exclusions. Professional services such as architecture, surveying, and consultancy are generally outside CIS, even if they relate to a construction project. Manufacturing materials off site is also usually excluded.

Understanding whether work falls within CIS is essential, because applying CIS incorrectly can create unnecessary administration and disputes.

Contractor obligations under CIS

If you are a contractor under CIS, you have several legal obligations. You must register with HMRC as a CIS contractor, verify subcontractors before paying them, deduct tax where required, submit monthly CIS returns, and pay deductions to HMRC on time.

Each subcontractor must be verified with HMRC to confirm the correct deduction rate. There are three possible outcomes:.

• 20 percent deduction for registered subcontractors

• 30 percent deduction for unregistered subcontractors

• 0 percent deduction for those approved for gross payment

The contractor must then deduct the correct amount from the labour element of the payment and report it to HMRC.

From experience, I can say that many contractor errors arise not from deliberate non compliance, but from misunderstanding who should be verified and what parts of an invoice are subject to deduction.

Subcontractor obligations under CIS

As a subcontractor, your main obligation is to register with HMRC for CIS and ensure your details are correct. If you are registered, deductions are normally made at 20 percent rather than 30 percent, which makes a significant difference to cash flow.

You also need to keep accurate records of income received and CIS deducted. These records are essential when it comes to reclaiming or offsetting deductions later.

Importantly, CIS does not remove your obligation to file tax returns. Whether you are self employed or running a limited company, you must still declare your income and expenses in the usual way.

How CIS deductions actually work

CIS deductions are made from the labour element of a payment, not from materials, VAT, or certain allowable costs. This is another area where mistakes are common.

For example, if a subcontractor invoices £5,000 labour and £2,000 materials plus VAT, the CIS deduction applies only to the £5,000 labour element. The contractor deducts 20 percent or 30 percent of that figure and pays the net amount to the subcontractor.

The deducted amount is then paid to HMRC and recorded against the subcontractor’s tax record.

This is why clear invoicing matters. If labour and materials are not separated, contractors may deduct CIS on the full amount, which can unfairly increase deductions.

Is CIS a tax

One of the most important points I always make is that CIS is not a separate tax. It is a deduction on account of tax.

This means that CIS deducted is effectively a prepayment towards your eventual tax bill. How that prepayment is used depends on your business structure.

For sole traders and partnerships, CIS deducted is offset against income tax and National Insurance through the Self Assessment tax return.

For limited companies, CIS deducted is offset against PAYE and National Insurance liabilities through payroll reporting.

Understanding this distinction changes how you view CIS. It is not money lost, provided your affairs are in order, but it does affect timing and cash flow.

CIS and sole traders

If you are self employed and working under CIS, deductions made by contractors are set against your personal tax liabilities.

When you complete your Self Assessment tax return, you declare your gross income, allowable expenses, and the CIS deducted. HMRC then calculates your actual tax liability. If CIS deducted exceeds the tax due, you receive a refund. If it is less, you pay the balance.

This is why many sole traders receive tax refunds each year under CIS, particularly if they have significant allowable expenses.

However, this only works if the tax return is completed accurately and on time. Missing CIS figures or incorrect income declarations can delay refunds significantly.

CIS and limited companies

Limited companies are treated differently. CIS deducted from company income is not reclaimed through a corporation tax return. Instead, it is offset against PAYE liabilities via the payroll system.

Each month, the company reports CIS suffered on its Employer Payment Summary, and HMRC reduces the PAYE bill accordingly.

If PAYE liabilities are low, CIS balances can build up, which is why salary planning often plays a role in managing CIS efficiently for limited companies.

This difference between sole traders and companies is one of the biggest sources of confusion I encounter.

Gross payment status under CIS

Some subcontractors can apply for gross payment status, which means they are paid in full without CIS deductions. To qualify, strict conditions must be met relating to turnover, compliance history, and tax payment behaviour.

Gross payment status can significantly improve cash flow, but it also places greater responsibility on the subcontractor to manage their own tax payments. Losing gross status can happen quickly if compliance slips.

From experience, applying for gross status makes sense only once a business is well organised and consistently compliant.

CIS and VAT

CIS and VAT are separate systems, but they interact in practice.

VAT is charged and paid in the normal way, regardless of CIS. CIS deductions are calculated on amounts excluding VAT. The subcontractor still receives VAT in full, and the contractor reclaims it if registered.

This separation is logical, but it does mean that subcontractors must be careful not to confuse VAT receipts with income that has already been taxed.

Common CIS misunderstandings

There are several myths around CIS that persist despite clear HMRC guidance.

One is that CIS replaces Self Assessment. It does not.

Another is that CIS deductions are the final tax bill. They are not.

There is also a belief that being under CIS automatically means you are self employed. Employment status is determined by working arrangements, not by CIS alone.

These misunderstandings can lead to compliance issues if left unaddressed.

Record keeping under CIS

Good record keeping under CIS is essential. You should retain payment statements, invoices, and confirmation of deductions. These documents support your tax returns and help resolve disputes if HMRC records do not match yours.

From a practical point of view, reconciling CIS monthly rather than annually reduces stress and avoids surprises.

Why CIS affects cash flow so much

The biggest real world impact of CIS is on cash flow. Money is deducted before you see it, often months before your final tax position is known.

For businesses with tight margins, this can create pressure, particularly if deductions are high or applied incorrectly. Understanding CIS helps you plan pricing, budgeting, and tax payments more realistically.

How CIS fits into the wider tax system

CIS does not operate in isolation. It links directly to income tax, National Insurance, PAYE, corporation tax, and VAT.

When understood as part of that wider system, CIS becomes less intimidating and more predictable. When treated as a standalone tax, it often feels arbitrary and unfair.

Why CIS still matters today

Despite ongoing discussions about tax reform and digital reporting, CIS remains a central feature of the UK construction industry. It reflects the unique nature of the sector and the need for early tax collection.

For those working in construction, understanding CIS is not optional. It affects earnings, compliance, and long term financial planning.

Final thoughts

CIS is often described as complicated, but in reality it is logical once you understand its purpose. It is a system designed to collect tax earlier, not to increase the amount of tax you pay.

In my experience, most problems with CIS arise not from the rules themselves, but from misunderstanding how deductions are later reconciled. With clear records, correct registration, and timely reporting, CIS becomes a manageable part of working in construction rather than a constant frustration.

If there is one thing I would encourage anyone in the industry to do, it is to invest time in understanding CIS properly. It pays dividends in reduced stress, better cash flow, and fewer unpleasant surprises from HMRC.

You may also find our guidance on what is cis registered and how does cis work helpful when dealing with related CIS questions. For a broader overview of CIS rules, compliance, and support, you can visit our CIS guidance hub.